Opportunities for Pumice resource
development in Ethiopia
Geoscience Data Center,
Geological Survey of Ethiopia,
November 2011.
Pumice resource potential of Ethiopia
November 2011
lar glass generally composed of 60-70% SiO2, 1214% Al2O3, 1-2% Fe2O3 and alkali oxides (Mengistu
and Fantaw, 2003). Pumice has generally a specific
gravity of <1%.
1. Introduction
Pumice is a textural term for a volcanic rock that is
solidified frothy lava typically created when superheated, highly pressurized rock is violently ejected
from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the
simultaneous actions of rapid cooling and rapid depressurization (Carr, 1994). The depressurization creates bubbles by lowering the solubility of gases
(including water and CO2) dissolved in the lava,
causing the gases to rapidly exsolve (like the bubbles
of CO2 that appear when a carbonated drink is
opened). The simultaneous cooling and depressurization freezes the bubbles in the matrix and creates
vesicles (Figure 1).
Figure 2 Fine grained, light grey pumice (Adami Tulu,
South Shoa Zone). Photograph: By Sentayehu Zewdie
1.1 End Use
Pumice has good thermal and sound insulation properties. It has very low permeability and adequate
compressive strength and modules of elasticity and
hence can be used for stucco and plaster aggregate
(Figure 3).
Figure 1 Voids in pumice resulted from depressurization that
creates bubbles (Fentale).Photograph: By Sentayehu Zewdie
Pumice is formed when lava cooled quickly above
ground. You can see where little pockets of air had
been. This rock is so light, that many pumice rocks
will actually float in water.
Pumice is actually a kind of glass and not a mixture
of minerals. Pumice is a light colored highly vesicu-
Figure 3. Pumice used as stucco and plaster aggregate in walls
and ceilings living room.
1
Pumice resource potential of Ethiopia
November 2011
With the continuing increase in energy cost, pumice
is a natural insulator both in heat or cooling and
sound.
Where an "R" value is required, Pumice provides
significantly greater thermal resistance when compared to regular weight concrete. This inert, durable,
stable, free-draining and environmentally "friendly"
lightweight aggregate is extremely easy to handle
and provides economical long term solutions for precast challenges.
Pumice is widely used to make lightweight concrete
or isolative low-density breeze blocks. When used as
an additive for cement, a fine-grained version of
pumice called pozzolan is mixed with lime to form a
light-weight, smooth, plaster-like concrete.
Pumice Lightweight Aggregate has a long track record of quality and performance. Since it development in the early nineteen hundreds, Pumice structural lightweight concrete has been used extensively
in high-rise buildings, commercial buildings, hospitals, and schools, government housing and major
shopping centers. Pumice aggregate is also used in
precast, pre-stressed concrete, masonry and geotechnical applications (Figure 5).
This form of concrete was used as far back as Roman
times. Roman engineers used it to build the huge
dome of the Pantheon and as construction material
for many aqueducts.
Because this rock is so light, it is used quite often as
a decorative landscape stone. Ground to a powder, it
is used as an abrasive in polish compounds and in
Lava soap.
For almost 50 years, Pumice Lightweight Aggregate has been effectively used to replace heavy
weight concrete products with lightweight concretes.
Lightweight pumice aggregate can reduce the weight
of precast by up to one-half.
Pumice can also be used in Pozolana Portland cement (PPC) to produce concrete. About 25 to 28%
pumice is required during grinding of clinker for production of pozzolanic cement (Figure 4).
Figure 5 Outcrop of fine aggregate (pumicite).(Alemtena).
Photograph: By Sentayehu Zewdie
The quality of Lightweight Aggregate results from a
carefully controlled screening operation. The result is
a high-quality, lightweight aggregate that is inert,
durable, tough, stable, highly isolative, and ready to
meet stringent specifications for most structural and
non-structural lightweight concrete projects.
It is also used as an abrasive, especially in polishes,
pencil erasers, cosmetic exfoliants, and the production of stone-washed jeans. "Pumice stones" are often used in beauty salons during the pedicure process
to remove dry and excess skin from the bottom of the
Figure 4 Pozolana Portland Cement produced from 25-28%
of pumice
2
Pumice resource potential of Ethiopia
November 2011
foot as well as calluses. It was also used in ancient
Greek and Roman times to remove excess hair
(Figure 6).
Figure 8 Pumice and pumicite used in hand soaps as mild
abrasive.
Figure 6 Smooth and fine grained pumice used as removing
hair and dead skin from leg.
Pumice is also used as a growing substrate for growing horticultural crops especially in hot areas where
evapo-teranspiration is high (Figure 7).
Finely ground pumice is added to some toothpastes
and heavy-duty hand cleaners (Figure 9)
Figure 9 finely ground pumice are added to toothpaste.
Photograph: by sentayehu zewdie
Figure 7 Pumice and scoria aggregates with selected size can
be used as rock mulching to retain moisture and re
duce evaporation in hot climate (Rift Valley).
Photograph : By Sentayehu Zewdie
When the vesicles are interconnected they can be
used as absorbent. Fine ground high-purity pumice
can be processed into various particle size suitable
for fillers.
Since pumice and pumicite are inert (pH=7.2) and
extremely brittle they can be used as a mild abrasives
in hand soaps, stone-washed jeans, grill cleaners etc.,
(Mengistu and Fantaw, 2003) (Figure 8).
The use of lightweight concrete was used in ancient
Rome over 2000 years ago. The construction of the
Pantheon, the Coliseum, the Immense Valts of the
3
Pumice resource potential of Ethiopia
November 2011
public bath and many other structures still standing
today.
The pumice block is similar, except that the sand and gravel is
replaced with lightweight pumice course aggregate. This
blend of aggregate is sometimes referred to as a semilightweight block when the total aggregate consists of pumice
and cement, then it is referred to as lightweight block and is one
half the weight of standard block (Figure 10) .
Figure 11. Different kind of pumice with different colors,
textures, and sizes to meet the needs of many architectural
applications (Alemtena Pumice) :
Photograph by: Sentayehu zewdie
2. Geology
Pumice is composed of highly micro vesicular glass
pyroclastic with very thin, translucent bubble walls
of extrusive igneous rock. It is commonly, but not
exclusively of silicic or felsic to intermediate in composition (e.g., rhyolitic, dacitic, andesite, pantellerite,
phonolite, trachyte), but basaltic and other compositions are known. Pumice is commonly pale in color,
ranging from white, cream, blue or grey, to greenbrown or black (Figure 12). It forms when volcanic
gases exsolving from viscous magma nucleate bubbles which cannot readily decouple from the viscous
magma prior to chilling to glass. Pumice is a common product of explosive eruptions (ignimbriteforming) and commonly forms zones in upper parts
of silicic lavas. Pumice has an average porosity of
90%, and initially floats on water.
Figure 10 Pumice is a raw material for Light weight
aggregate. (Alemtena) Photograph: by sentayehu
Tufflite is a strong, durable, porous glass pumice aggregate of volcanic origin, and an ideal natural material for use in structural lightweight concrete. With
the continuing increase in energy cost, the use of
natural aggregate marks a return to the economic
principles as associated with the use of lightweight
concrete.
Stone veneer that is made from pumice is lightweight
and can be installed on almost any surface. Stone veneer is available in many different colors, textures,
and sizes to meet the needs of many architectural applications (Figure 11).
4
Pumice resource potential of Ethiopia
November 2011
Figure 13 Outcrop of pumice, consist of subspherical
to spherical vesicles. (Alemtena).
Figure 12 Light grey, fine grained pumice (Meki).
Photograph: by sentayehu zewdie .
Photograph: by sentayehu zewdie
In Ethiopia pumice occurs in the Main Ethiopia Rift
valley associated with Aden series volcanic
(Kazmine, 1975) (Figure 14).
Scoria differs from pumice in being denser. With larger vesicles and thicker vesicle walls, it sinks rapidly. The difference is the result of the lower viscosity of the magma that forms scoria. When larger
amounts of gas are present, the result is a finergrained variety of pumice known as pumicite. Pumice is considered a glass because it has no crystal
structure. Pumice varies in density according to the
thickness of the solid material between the bubbles;
many samples float in water.
Splitting the country into two parts and running NNE
-SSW, the East –African Rift Valley stands out to be
one of the geological active zones in the world. In
Africa the rift extends over 1000km in NE direction
from Kenyan border to the Afar Depression and covers an area of about 150,000km2.
The East Africa Rift originated during the Late Tertiary time with extensive out pouring of basaltic lavas
and eruption of large quantity of pyroclastic flows,
forming the Trap Series (Bates, 1969).
There are two main forms of vesicles. Most pumice
contains tubular microvesicles that can impart a silky
or fibrous fabric. The elongation of the microvesicles
occurs due to ductile elongation in the volcanic conduit or, in the case of pumiceous lavas, during flow.
The other form of vesicles is subspherical to spherical and results from high vapor pressure during eruption (Figure 13).
During the Late Tertiary, the up –swelling of the
axial part of the volcanic plateau formed by the Trap
Series was accompanied by the tectonic fragmentation and collapse of Rift Valley (Kazmine, 1972).
The latter was probably filled by both fissurral and
central volcanic products known as the rift series
where pyoclastic rocks including pumice occur.
5
Pumice resource potential of Ethiopia
November 2011
Figure 14 Geological map of Ethiopia showing Mid-Upper Tertiary volcanic along Main Ethiopian Rift
6
Pumice resource potential of Ethiopia
November 2011
kilometers west of Nazareth along the NazarethAddis Ababa road, near the Ethiopia leather factory,
3. Pumice Occurence in Ethiopia
According to the local farmers, deposit has been
quarried for long time (Figure 17 and Figure 20 and
Table 1).
The East African rift valley originated during Late
Tertiary with expansive out pouring of lava and pyroclastic flow forming pumicite and pumicious ash in
the Main Ethiopian Rift Valley (MERV).
It is approximately 500 meters long 5 meters wide
and 3 meters deep; 7,500 cubic meters (Asefa, 1976).
Although, there are a lot of occurrences of pumice
in the MERV, the best known deposits are Gari Baldi
Pass, Koka, Dere, Bishoftu, Modjo, Alemtena and
Meki (Mengistu and Fantaw, 2003). Fentale, Lake
Verdi and Kinbibit are not studied well (Murdock,
1994). Occurrences are also found in Adami-Tulu
and Langano (Figure 15 and 16).
Figure 17 Pumice quarry at Alemtena.
Photograph: by sentayehu zewdie
3.2 Bishofetu
Figure 15. Out crop of pumice (Langano).
The Bishofetu pumice is located in the south of
Dbrezeyit Town about 15km to the south.
The main geological units exposed are pyroclastic
falls comprising of dominantly pumice and subordinate pumiceous ashes inter layers. The pumice deposit covers extensive area of variable thickens of
overburden which is commonly soil cover fluvial,
Figure 16 Grey fine grained pumice in Adami Tulu.
colluvial and debris (Figure 18). No detail work un-
3.1 Kimbibit
dertaken to get the reserve.
The Kinbibit pumice is located at 08°32’00"-8°
32’25N and 39°13’22’’-39°3’45"E, and lies five
7
Pumice resource potential of Ethiopia
November 2011
Figure 18 pumice outcrop, Bishoftu.
Photograph: by sentayehu zewdie
3.3. Koka, Alemtena and Meki
Figure 19. Thick Pumice outcrop (Meki and Alemtena).
Alemtena, Koka and Meki Pumice are located
Photograph: by sentayehu zewdie
around Koka, Meki and Alemtena towns in south
Shoa zone., Oromiya Regional State (Figure 20 and
Table 1).
Opportunity
The pumice is a high volcanic glass and usually
Although pumice is widespread in
rhyoitic, dacitic or trachytic in composition. It is light
Ethiopia, it is utilized only in limited
colored composed of fine ash.
areas for the purpose of cement and
block production.
The grain size of the particle throw out of the volcano diminish with distance from the eruption center
There is also an opportunity for the
as the particle thrown out of volcano one go away
from the source .these deposit composed of ash and
investors
to
conduct
fine grained pumice beds which indicate that the
prospecting and exploration in the areas
source of the ash is far compared to the coarser vari-
of Fentale, Meki, Adami Tulu and
ety (Figure 19). Extents and reserves of the deposit is
Bishoftu and other rift valley areas to
not known.
mine pumice for cosmetics and other
industrial purposes.
8
systematic
Pumice resource potential of Ethiopia
November 2011
Table 1. Location of pumice deposit in Ethiopia
Points
x
Y
Localities
1
593864
994942
Fentale
2
594362
995014
Fentale
3
595305
994746
Fentale
4
595477
994565
Fentale
5
577709
962005
Fentale
6
498000
957000
Bishoftu
7
491499
913669
Alem Tena
8
496240.3
957793.2
lake Verdi
9
506785.6
943052.9
Kinbibit
Figure 20. Location map of pumice
deposits in Ethiopia.
9
Pumice resource potential of Ethiopia
November 2011
References
Asefa, A. 1976. Pumice at Kinbibit. Unpublished
technical report EIGS, Addis Ababa.
Bates, R. 1969. Geology of the Industrial Rocks and
Minerals.
Carr, D. 1994. Industrial Minerals and Rocks. 6th
Edition. Society for Mining, Metallurgy and
Exploration, Inc. Littieton, Colorado.
Kazmin, V. 1972. Geology of Ethiopia Unpublished
report EIGS Addis Ababa. Ethiopia.
Kazmin, V. 1975, Explanation of the Geological
Map of Ethiopia.
Lorenz, W., Gwosdz, W. 2003. Manual on the Geological-technical Assessment of Mineral Construction Materials. Geologisches Jahrbuch, Sonderhefte
Reihe H, Heft SH 15. Germany, Hannover.
Murdock, T.G. 1994. Pumice Deposit in Lake Verdi.
10
Pumice resource potential of Ethiopia
November 2011
als locally or abroad giving marketing freedom;
About the Ministry of Mines
• Provides for exemptions from custom duties and
taxes on equipment, machinery, vehicles and spare
parts;
In compliance with the market oriented economic policy of Ethiopia, the parliament declared that it is the
continuing policy of the Federal Government in the
national interest to foster and encourage private enterprises in developing economically sound and stable
mineral mining.
• Gives securities of tenure;
• Gives clear provisions on fiscal and other issues;
• Considering taxation on repatriation of profits and
capitals, a licensee shall pay a 2-5% royalty on ad
Val Orem at production site, and a 35% income
tax on taxable income. Taxable income is computed
by subtracting from gross income for any accounting year all allowable revenue expenditure, a four
years straight line depreciation, reinvestment deduction and permitted loses; and
Accordingly, the Federal Government’s Ministry of
Mines and Energy is responsible to administer and
supervise all large scale mining operations including
issuing prospecting, exploration and mining licenses
for foreign investors and to these in joint venture with
Ethiopians as per the reform issued in 1998 on the
Mining proclamation following the realization of previous shortcomings of earlier laws and policies.
• The mining proclamation guarantees the opening
and operation of a foreign currency account in
banks in Ethiopia, retention of portion of foreign
currency earning and remittances of profits, dividends, principal and interest on a foreign loan etc.
out of Ethiopia.
The reform clearly stipulated the responsibility of National Regional Governments to issue licenses and
administer all small scale mining operations owned by
Ethiopians and collecting all fees in addition to issue
prospecting and exploration licenses for national investors.
Of course this fiscal package is still subject to frequent
reviews for maintaining a balance between the objective of the government and investors as is evident by a
series of amendments of the 1993.
Mining Legislation
INVESTMENT CLIMATE OF ETHIOPIA
In June 1993 new Mining and Mining Income Tax
Proclamations were issued having considered knowledge-based experiences in some competitive countries
and given the following provisions;
The Federal Democratic Republic of Ethiopia has created a conducive investment environment to ensure
and promote private investment to play a leading role
in the development of the national economy.
• Invite private investment in all kinds of mineral
operations;
• Provides a prospecting license for one year;
This favorable climate for foreign investment has
been created as consequence of the solid foundation of
political and economic reform, particularly the stably
secured macroeconomic reforms which are achieved
by carefully managed sequential reforms coupled with
faire fiscal and monetary policies. By the virtues of
Ethiopia’s unique and untapped natural resources, its
• Provides an exploration license for an initial period
of three years and renewed twice for one year
each;
• Provides a mining license for 20 years and renewed
for 10 years unlimitedly;
• Guarantee the licensee’s right to sell all the miner11
Pumice resource potential of Ethiopia
November 2011
Kenticha Tantalum Mine which is already in the pipeline for privatization. This includes the reform of the
mining law which is taking place since 1993 and many
changes that have happened to justify the sincerity of
the government..
proximity to middle eastern and European markets,
its 60 million population, and huge labor force both
disciplined and easily trainable are some of the comparative advantages worthy of consideration while
investing in Ethiopia. This is further enhanced by specific incentives and efficient administrative procedures.
Furthermore the commitment is much affirmed following the establishment of a fair and clear cut mining legislation giving investors assurances of the fruits
of their success. It constitutes a fair setup of efficient
and effective licensing and mineral right administration system, a fair set of environmental laws, rules to
monitor and mitigate and reclamation effects by mining operation, fair laws to regulate the safety and
health of the work fore and securing of tenure. It also
gives freedom to license holders with a number of incentives including low royalty, exemption from custom duties and taxes on the equipment, machineries
vehicles, and spare parts necessary for mineral operations with a 10 years provision to allow investors to
carry forward losses.
Mineral Investment
Between 1974 and 1991 private investments were not
allowed in the mineral sector. The government was
fully responsible for the exploration and development
of the sector, before the advent of the new economic
policy of Ethiopia. In compliance with the new market
economic policy of Ethiopia the parliament declares
that it is continuing to update the policy of the Federal
Government in the national interest to foster and encourage private enterprises in developing economically sound and stable mineral mining.
For a successful implementation of the policy, a number of steps have been taken aiming to boost the confidence of the private sector following the government’s
strong believe that rapid mineral development can
only be realized when the private sector is given full
right of operating managing and owning mineral enterprises. This is the underlined reason for the government’s active response to the concern of the International mining Companies. Accordingly it has restricted its role to basic mineral resources exploration,
regulation and promotion only;
Prepared by Sentayehu Zewdie; sentayehuzewdie@yahoo/com Editing & layout by Geremew Negassa; [email protected] Geoscience Data Center,
Geological Survey of Ethiopia (GSE)
P.O.Box 2302, Addis Ababa, Ethiopia
to avoid the fear of controlling a large tract of prospective land by state owned companies, and to avoid
the fear of seeable high risk due to unexpected unfair
competition with state owned enterprises.
Tel: (251-1) 46 33 25
Fax: (251-1) 46 33 26, 71 20 33
Website: www.geology.gov.et
E-mail: [email protected]
In this connection a measure stick for such track record of the government’s commitment is manifested
by the privatized Lege Dembi Gold Mine, the only one
government owned large scale gold mining, and the
12
Pumice resource potential of Ethiopia
November 2011
lar glass generally composed of 60-70% SiO2, 1214% Al2O3, 1-2% Fe2O3 and alkali oxides (Mengistu
and Fantaw, 2003). Pumice has generally a specific
gravity of <1%.
1. Introduction
Pumice is a textural term for a volcanic rock that is
solidified frothy lava typically created when superheated, highly pressurized rock is violently ejected
from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the
simultaneous actions of rapid cooling and rapid depressurization (Carr, 1994). The depressurization creates bubbles by lowering the solubility of gases
(including water and CO2) dissolved in the lava,
causing the gases to rapidly exsolve (like the bubbles
of CO2 that appear when a carbonated drink is
opened). The simultaneous cooling and depressurization freezes the bubbles in the matrix and creates
vesicles (Figure 1).
Figure 2 Fine grained, light grey pumice (Adami Tulu,
South Shoa Zone). Photograph: By Sentayehu Zewdie
1.1 End Use
Pumice has good thermal and sound insulation properties. It has very low permeability and adequate
compressive strength and modules of elasticity and
hence can be used for stucco and plaster aggregate
(Figure 3).
Figure 1 Voids in pumice resulted from depressurization that
creates bubbles (Fentale).Photograph: By Sentayehu Zewdie
Pumice is formed when lava cooled quickly above
ground. You can see where little pockets of air had
been. This rock is so light, that many pumice rocks
will actually float in water.
Pumice is actually a kind of glass and not a mixture
of minerals. Pumice is a light colored highly vesicu-
Figure 3. Pumice used as stucco and plaster aggregate in walls
and ceilings living room.
1
Pumice resource potential of Ethiopia
November 2011
With the continuing increase in energy cost, pumice
is a natural insulator both in heat or cooling and
sound.
Where an "R" value is required, Pumice provides
significantly greater thermal resistance when compared to regular weight concrete. This inert, durable,
stable, free-draining and environmentally "friendly"
lightweight aggregate is extremely easy to handle
and provides economical long term solutions for precast challenges.
Pumice is widely used to make lightweight concrete
or isolative low-density breeze blocks. When used as
an additive for cement, a fine-grained version of
pumice called pozzolan is mixed with lime to form a
light-weight, smooth, plaster-like concrete.
Pumice Lightweight Aggregate has a long track record of quality and performance. Since it development in the early nineteen hundreds, Pumice structural lightweight concrete has been used extensively
in high-rise buildings, commercial buildings, hospitals, and schools, government housing and major
shopping centers. Pumice aggregate is also used in
precast, pre-stressed concrete, masonry and geotechnical applications (Figure 5).
This form of concrete was used as far back as Roman
times. Roman engineers used it to build the huge
dome of the Pantheon and as construction material
for many aqueducts.
Because this rock is so light, it is used quite often as
a decorative landscape stone. Ground to a powder, it
is used as an abrasive in polish compounds and in
Lava soap.
For almost 50 years, Pumice Lightweight Aggregate has been effectively used to replace heavy
weight concrete products with lightweight concretes.
Lightweight pumice aggregate can reduce the weight
of precast by up to one-half.
Pumice can also be used in Pozolana Portland cement (PPC) to produce concrete. About 25 to 28%
pumice is required during grinding of clinker for production of pozzolanic cement (Figure 4).
Figure 5 Outcrop of fine aggregate (pumicite).(Alemtena).
Photograph: By Sentayehu Zewdie
The quality of Lightweight Aggregate results from a
carefully controlled screening operation. The result is
a high-quality, lightweight aggregate that is inert,
durable, tough, stable, highly isolative, and ready to
meet stringent specifications for most structural and
non-structural lightweight concrete projects.
It is also used as an abrasive, especially in polishes,
pencil erasers, cosmetic exfoliants, and the production of stone-washed jeans. "Pumice stones" are often used in beauty salons during the pedicure process
to remove dry and excess skin from the bottom of the
Figure 4 Pozolana Portland Cement produced from 25-28%
of pumice
2
Pumice resource potential of Ethiopia
November 2011
foot as well as calluses. It was also used in ancient
Greek and Roman times to remove excess hair
(Figure 6).
Figure 8 Pumice and pumicite used in hand soaps as mild
abrasive.
Figure 6 Smooth and fine grained pumice used as removing
hair and dead skin from leg.
Pumice is also used as a growing substrate for growing horticultural crops especially in hot areas where
evapo-teranspiration is high (Figure 7).
Finely ground pumice is added to some toothpastes
and heavy-duty hand cleaners (Figure 9)
Figure 9 finely ground pumice are added to toothpaste.
Photograph: by sentayehu zewdie
Figure 7 Pumice and scoria aggregates with selected size can
be used as rock mulching to retain moisture and re
duce evaporation in hot climate (Rift Valley).
Photograph : By Sentayehu Zewdie
When the vesicles are interconnected they can be
used as absorbent. Fine ground high-purity pumice
can be processed into various particle size suitable
for fillers.
Since pumice and pumicite are inert (pH=7.2) and
extremely brittle they can be used as a mild abrasives
in hand soaps, stone-washed jeans, grill cleaners etc.,
(Mengistu and Fantaw, 2003) (Figure 8).
The use of lightweight concrete was used in ancient
Rome over 2000 years ago. The construction of the
Pantheon, the Coliseum, the Immense Valts of the
3
Pumice resource potential of Ethiopia
November 2011
public bath and many other structures still standing
today.
The pumice block is similar, except that the sand and gravel is
replaced with lightweight pumice course aggregate. This
blend of aggregate is sometimes referred to as a semilightweight block when the total aggregate consists of pumice
and cement, then it is referred to as lightweight block and is one
half the weight of standard block (Figure 10) .
Figure 11. Different kind of pumice with different colors,
textures, and sizes to meet the needs of many architectural
applications (Alemtena Pumice) :
Photograph by: Sentayehu zewdie
2. Geology
Pumice is composed of highly micro vesicular glass
pyroclastic with very thin, translucent bubble walls
of extrusive igneous rock. It is commonly, but not
exclusively of silicic or felsic to intermediate in composition (e.g., rhyolitic, dacitic, andesite, pantellerite,
phonolite, trachyte), but basaltic and other compositions are known. Pumice is commonly pale in color,
ranging from white, cream, blue or grey, to greenbrown or black (Figure 12). It forms when volcanic
gases exsolving from viscous magma nucleate bubbles which cannot readily decouple from the viscous
magma prior to chilling to glass. Pumice is a common product of explosive eruptions (ignimbriteforming) and commonly forms zones in upper parts
of silicic lavas. Pumice has an average porosity of
90%, and initially floats on water.
Figure 10 Pumice is a raw material for Light weight
aggregate. (Alemtena) Photograph: by sentayehu
Tufflite is a strong, durable, porous glass pumice aggregate of volcanic origin, and an ideal natural material for use in structural lightweight concrete. With
the continuing increase in energy cost, the use of
natural aggregate marks a return to the economic
principles as associated with the use of lightweight
concrete.
Stone veneer that is made from pumice is lightweight
and can be installed on almost any surface. Stone veneer is available in many different colors, textures,
and sizes to meet the needs of many architectural applications (Figure 11).
4
Pumice resource potential of Ethiopia
November 2011
Figure 13 Outcrop of pumice, consist of subspherical
to spherical vesicles. (Alemtena).
Figure 12 Light grey, fine grained pumice (Meki).
Photograph: by sentayehu zewdie .
Photograph: by sentayehu zewdie
In Ethiopia pumice occurs in the Main Ethiopia Rift
valley associated with Aden series volcanic
(Kazmine, 1975) (Figure 14).
Scoria differs from pumice in being denser. With larger vesicles and thicker vesicle walls, it sinks rapidly. The difference is the result of the lower viscosity of the magma that forms scoria. When larger
amounts of gas are present, the result is a finergrained variety of pumice known as pumicite. Pumice is considered a glass because it has no crystal
structure. Pumice varies in density according to the
thickness of the solid material between the bubbles;
many samples float in water.
Splitting the country into two parts and running NNE
-SSW, the East –African Rift Valley stands out to be
one of the geological active zones in the world. In
Africa the rift extends over 1000km in NE direction
from Kenyan border to the Afar Depression and covers an area of about 150,000km2.
The East Africa Rift originated during the Late Tertiary time with extensive out pouring of basaltic lavas
and eruption of large quantity of pyroclastic flows,
forming the Trap Series (Bates, 1969).
There are two main forms of vesicles. Most pumice
contains tubular microvesicles that can impart a silky
or fibrous fabric. The elongation of the microvesicles
occurs due to ductile elongation in the volcanic conduit or, in the case of pumiceous lavas, during flow.
The other form of vesicles is subspherical to spherical and results from high vapor pressure during eruption (Figure 13).
During the Late Tertiary, the up –swelling of the
axial part of the volcanic plateau formed by the Trap
Series was accompanied by the tectonic fragmentation and collapse of Rift Valley (Kazmine, 1972).
The latter was probably filled by both fissurral and
central volcanic products known as the rift series
where pyoclastic rocks including pumice occur.
5
Pumice resource potential of Ethiopia
November 2011
Figure 14 Geological map of Ethiopia showing Mid-Upper Tertiary volcanic along Main Ethiopian Rift
6
Pumice resource potential of Ethiopia
November 2011
kilometers west of Nazareth along the NazarethAddis Ababa road, near the Ethiopia leather factory,
3. Pumice Occurence in Ethiopia
According to the local farmers, deposit has been
quarried for long time (Figure 17 and Figure 20 and
Table 1).
The East African rift valley originated during Late
Tertiary with expansive out pouring of lava and pyroclastic flow forming pumicite and pumicious ash in
the Main Ethiopian Rift Valley (MERV).
It is approximately 500 meters long 5 meters wide
and 3 meters deep; 7,500 cubic meters (Asefa, 1976).
Although, there are a lot of occurrences of pumice
in the MERV, the best known deposits are Gari Baldi
Pass, Koka, Dere, Bishoftu, Modjo, Alemtena and
Meki (Mengistu and Fantaw, 2003). Fentale, Lake
Verdi and Kinbibit are not studied well (Murdock,
1994). Occurrences are also found in Adami-Tulu
and Langano (Figure 15 and 16).
Figure 17 Pumice quarry at Alemtena.
Photograph: by sentayehu zewdie
3.2 Bishofetu
Figure 15. Out crop of pumice (Langano).
The Bishofetu pumice is located in the south of
Dbrezeyit Town about 15km to the south.
The main geological units exposed are pyroclastic
falls comprising of dominantly pumice and subordinate pumiceous ashes inter layers. The pumice deposit covers extensive area of variable thickens of
overburden which is commonly soil cover fluvial,
Figure 16 Grey fine grained pumice in Adami Tulu.
colluvial and debris (Figure 18). No detail work un-
3.1 Kimbibit
dertaken to get the reserve.
The Kinbibit pumice is located at 08°32’00"-8°
32’25N and 39°13’22’’-39°3’45"E, and lies five
7
Pumice resource potential of Ethiopia
November 2011
Figure 18 pumice outcrop, Bishoftu.
Photograph: by sentayehu zewdie
3.3. Koka, Alemtena and Meki
Figure 19. Thick Pumice outcrop (Meki and Alemtena).
Alemtena, Koka and Meki Pumice are located
Photograph: by sentayehu zewdie
around Koka, Meki and Alemtena towns in south
Shoa zone., Oromiya Regional State (Figure 20 and
Table 1).
Opportunity
The pumice is a high volcanic glass and usually
Although pumice is widespread in
rhyoitic, dacitic or trachytic in composition. It is light
Ethiopia, it is utilized only in limited
colored composed of fine ash.
areas for the purpose of cement and
block production.
The grain size of the particle throw out of the volcano diminish with distance from the eruption center
There is also an opportunity for the
as the particle thrown out of volcano one go away
from the source .these deposit composed of ash and
investors
to
conduct
fine grained pumice beds which indicate that the
prospecting and exploration in the areas
source of the ash is far compared to the coarser vari-
of Fentale, Meki, Adami Tulu and
ety (Figure 19). Extents and reserves of the deposit is
Bishoftu and other rift valley areas to
not known.
mine pumice for cosmetics and other
industrial purposes.
8
systematic
Pumice resource potential of Ethiopia
November 2011
Table 1. Location of pumice deposit in Ethiopia
Points
x
Y
Localities
1
593864
994942
Fentale
2
594362
995014
Fentale
3
595305
994746
Fentale
4
595477
994565
Fentale
5
577709
962005
Fentale
6
498000
957000
Bishoftu
7
491499
913669
Alem Tena
8
496240.3
957793.2
lake Verdi
9
506785.6
943052.9
Kinbibit
Figure 20. Location map of pumice
deposits in Ethiopia.
9
Pumice resource potential of Ethiopia
November 2011
References
Asefa, A. 1976. Pumice at Kinbibit. Unpublished
technical report EIGS, Addis Ababa.
Bates, R. 1969. Geology of the Industrial Rocks and
Minerals.
Carr, D. 1994. Industrial Minerals and Rocks. 6th
Edition. Society for Mining, Metallurgy and
Exploration, Inc. Littieton, Colorado.
Kazmin, V. 1972. Geology of Ethiopia Unpublished
report EIGS Addis Ababa. Ethiopia.
Kazmin, V. 1975, Explanation of the Geological
Map of Ethiopia.
Lorenz, W., Gwosdz, W. 2003. Manual on the Geological-technical Assessment of Mineral Construction Materials. Geologisches Jahrbuch, Sonderhefte
Reihe H, Heft SH 15. Germany, Hannover.
Murdock, T.G. 1994. Pumice Deposit in Lake Verdi.
10
Pumice resource potential of Ethiopia
November 2011
als locally or abroad giving marketing freedom;
About the Ministry of Mines
• Provides for exemptions from custom duties and
taxes on equipment, machinery, vehicles and spare
parts;
In compliance with the market oriented economic policy of Ethiopia, the parliament declared that it is the
continuing policy of the Federal Government in the
national interest to foster and encourage private enterprises in developing economically sound and stable
mineral mining.
• Gives securities of tenure;
• Gives clear provisions on fiscal and other issues;
• Considering taxation on repatriation of profits and
capitals, a licensee shall pay a 2-5% royalty on ad
Val Orem at production site, and a 35% income
tax on taxable income. Taxable income is computed
by subtracting from gross income for any accounting year all allowable revenue expenditure, a four
years straight line depreciation, reinvestment deduction and permitted loses; and
Accordingly, the Federal Government’s Ministry of
Mines and Energy is responsible to administer and
supervise all large scale mining operations including
issuing prospecting, exploration and mining licenses
for foreign investors and to these in joint venture with
Ethiopians as per the reform issued in 1998 on the
Mining proclamation following the realization of previous shortcomings of earlier laws and policies.
• The mining proclamation guarantees the opening
and operation of a foreign currency account in
banks in Ethiopia, retention of portion of foreign
currency earning and remittances of profits, dividends, principal and interest on a foreign loan etc.
out of Ethiopia.
The reform clearly stipulated the responsibility of National Regional Governments to issue licenses and
administer all small scale mining operations owned by
Ethiopians and collecting all fees in addition to issue
prospecting and exploration licenses for national investors.
Of course this fiscal package is still subject to frequent
reviews for maintaining a balance between the objective of the government and investors as is evident by a
series of amendments of the 1993.
Mining Legislation
INVESTMENT CLIMATE OF ETHIOPIA
In June 1993 new Mining and Mining Income Tax
Proclamations were issued having considered knowledge-based experiences in some competitive countries
and given the following provisions;
The Federal Democratic Republic of Ethiopia has created a conducive investment environment to ensure
and promote private investment to play a leading role
in the development of the national economy.
• Invite private investment in all kinds of mineral
operations;
• Provides a prospecting license for one year;
This favorable climate for foreign investment has
been created as consequence of the solid foundation of
political and economic reform, particularly the stably
secured macroeconomic reforms which are achieved
by carefully managed sequential reforms coupled with
faire fiscal and monetary policies. By the virtues of
Ethiopia’s unique and untapped natural resources, its
• Provides an exploration license for an initial period
of three years and renewed twice for one year
each;
• Provides a mining license for 20 years and renewed
for 10 years unlimitedly;
• Guarantee the licensee’s right to sell all the miner11
Pumice resource potential of Ethiopia
November 2011
Kenticha Tantalum Mine which is already in the pipeline for privatization. This includes the reform of the
mining law which is taking place since 1993 and many
changes that have happened to justify the sincerity of
the government..
proximity to middle eastern and European markets,
its 60 million population, and huge labor force both
disciplined and easily trainable are some of the comparative advantages worthy of consideration while
investing in Ethiopia. This is further enhanced by specific incentives and efficient administrative procedures.
Furthermore the commitment is much affirmed following the establishment of a fair and clear cut mining legislation giving investors assurances of the fruits
of their success. It constitutes a fair setup of efficient
and effective licensing and mineral right administration system, a fair set of environmental laws, rules to
monitor and mitigate and reclamation effects by mining operation, fair laws to regulate the safety and
health of the work fore and securing of tenure. It also
gives freedom to license holders with a number of incentives including low royalty, exemption from custom duties and taxes on the equipment, machineries
vehicles, and spare parts necessary for mineral operations with a 10 years provision to allow investors to
carry forward losses.
Mineral Investment
Between 1974 and 1991 private investments were not
allowed in the mineral sector. The government was
fully responsible for the exploration and development
of the sector, before the advent of the new economic
policy of Ethiopia. In compliance with the new market
economic policy of Ethiopia the parliament declares
that it is continuing to update the policy of the Federal
Government in the national interest to foster and encourage private enterprises in developing economically sound and stable mineral mining.
For a successful implementation of the policy, a number of steps have been taken aiming to boost the confidence of the private sector following the government’s
strong believe that rapid mineral development can
only be realized when the private sector is given full
right of operating managing and owning mineral enterprises. This is the underlined reason for the government’s active response to the concern of the International mining Companies. Accordingly it has restricted its role to basic mineral resources exploration,
regulation and promotion only;
Prepared by Sentayehu Zewdie; sentayehuzewdie@yahoo/com Editing & layout by Geremew Negassa; [email protected] Geoscience Data Center,
Geological Survey of Ethiopia (GSE)
P.O.Box 2302, Addis Ababa, Ethiopia
to avoid the fear of controlling a large tract of prospective land by state owned companies, and to avoid
the fear of seeable high risk due to unexpected unfair
competition with state owned enterprises.
Tel: (251-1) 46 33 25
Fax: (251-1) 46 33 26, 71 20 33
Website: www.geology.gov.et
E-mail: [email protected]
In this connection a measure stick for such track record of the government’s commitment is manifested
by the privatized Lege Dembi Gold Mine, the only one
government owned large scale gold mining, and the
12