B"H
Hibonite
Properties and Terrestrial Occurrence
Griffin, W. L. (1), Toledo, V. (2), Gain, S.E.M. (1), Huang, J-X. (1)
1.
2.
ARC Centre of Excellence for Core to Crust Fluid Systems and GEMOC, Macquarie University, NSW
2109, Australia
Shefa Yamim (A.T.M.) Ltd., Akko, Israel
Composition: CaAl12O19: Al2O3 ca 85%, CaO 8% by weight. Substitution of Ce, La, Mg, Fe, Ti, Si,
giving (Ca,Ce)(Al,Ti,Mg,Fe)12O19.
Crystal Structure
Hexagonal - Dihexagonal Dipyramidal Space Group: P 63/mmc
Properties
Cleavage:
Color:
Density:
Diaphaneity:
Fracture:
Habit:
Hardness:
Luster:
Refractive index:
Streak:
Dichroism (e):
Dichroism (w):
Optical Data:
{0001} good
Yellow to red-brown to black.
3.84
Transparent to Opaque
Subconchoidal
Prisms, platy on {0001}, steep pyramids to several cm
7.5-8
Vitreous
1.790-1.807
brown
Uniaxial (-),ε = 1.79(1) . ω = 1.807(2)
The
historical
background
of
Hibonite, and its use as a gemstone
The mineral is named after Paul Hibon, who
found cm-sized black crystals in a placer
deposit in Madagascar in 1953, and sent them
to Jean Behier for examination. After further
analysis by C. Gillemin at the Sorbonne, It was
described as a new mineral in 1956 (Curien et
al., Am. Min, V. 42, p. 119).
confined to microscopic grains; it is one of the
oldest minerals in the solar system, and may
occur in interstellar dust.
Later on hibonite was assigned as a common
constituent of refractory Calcium-Aluminum
Inclusions in meteorites, mainly carbonaceous
chondrites. Meteoritic hibonite is blue, and
Type Locality
The type locality is the Esiva eluvials, Esiva,
Maromby Commune, Tulear Province,
Madagascar. The type material was probably
derived from nearby skarn deposits.
October, 2016
Its use as a gemstone has been limited, and
largely confined to placer material from
Myanmar, which yields transparent yellow
crystals up to 1-2 cm across.
Page 1 from 9
Occurrence
1.
2.
3.
Hibonite occurs frequently in thorianitebearing skarns, which are widespread in
Pan-African (565-515 Ma) granulites in
belts extending through Madagascar
(including the type locality) and
Tanzania. At least 20 localities are
known in Madagascar, with hibonite
crystals up to 10 cm long. It also occurs
in xenoliths of Ca-Al granulites brought
up in basanites in the Chyulu Hills
Volcanic Field in Kenya, also part of the
Pan-African belt. In the thorianitebearing skarns, which form metasomatic
lenses in C-Al rich rocks, probably
originally anorthosites. Usually early
corundum + spinel + scapolite
asemblages are altered to anorthite
+calcite+ scapolite, and hibonite
crystallizes at the expense of corundum
and spinel. P-T conditions are estimated
at 700-800 °C, 3.5 kbar.
The
crystallization of hibonite implies a very
low silica activity and probably high CO2.
Hibonite has been reported as blackbrown tabular crystals up to 3 cm across
in calcitic marbles from the TashelgaMalzaskaya region in Siberia. These
hibonites are notably high in Fe3+, and
V-rich minerals (goldmanite, tashelgite,
mukhinite….) are found in the same
rocks.
The Hatrurim formation (formerly
known as the “Mottled Zone”) is a
unique rock complex exposed mainly in
the Judean Desert. It was depsoited as a
thin marine, bituminous chalk-marl
formation of Campanian to Neogene
age.
Some parts of the Ghareb
formation contain up to 26% organic
matter and can be classified as oil shales.
Today the rocks in a number of areas,
especially the Jerusalem-Jericho area,
are largely composed of hightemperature metamorphic minerals
corresponding to the sanidinite and
pyroxene-hornfels facies (up to 1000 °C,
very low P). However, there is no
indication of igneous activity or contact
October, 2016
metamorphism in the area. The origin of
the heat which metamorphosed these
rocks is thought to be due to
spontaneous isochemical combustion of
bituminous compounds. The intensity of
metamorphism correlates to access to
oxygen; hydrocarbons are widespread in
surrounding rocks but are absent in the
metamorphosed beds. One paper argues
that
combustion
was
due
to
hydrocarbon fluids and heat released
from a “fossil mud volcano”.
The
rationale for this interpretation is not
clear. “Hatrurim Formation" is often
used as a locality name, but it is really a
geological unit, outcropping at many
localities, spread over three countries.
Gross (1977) did not describe hibonite
from Hatrurium formation, but it now
appears in most mineral lists from the
area.
4. Hibonite has recently been reported as
two transparent orange-brown crystals
(0.23, 0.71 gm) said to be recovered
from the gem gravels of Myamar.
There is no other information, but
other gems from these placers are
derived
from
high-temperature
granulite-facies
carbonate
rocks,
similar to those in Madagascar.
However, like the SY hibonite (see
below) the Myanmar material has very
low contents of Fe, but Ti and Mg are
both present at levers of 4-5 wt%
oxide. This distinguishes it from most
of the hibonite found in granulitefacies rocks. The Myanmar grains also
contain inclusions of corundum and
fluorite, giving another link to the SY
occurrences.
5. Hibonite is present in two forms in SY
samples: one type is found in primary
sources of Mt. Carmel and the other is
alluvial, recovered from the Kishon
catchment, the main drainage in
northern Israel (1022 sq km, 77 km
long). This catchment has been divided
in the SY Geological model iinto three
segments: Proximal, Mid, Distal
Reaches.
Page 2 from 9
6.
7.
8.
In the framework of mineralogical
analysis of target minerals from these
localities within SY's exploration permit
areas, SY sent what was then recognized
as corundum of Non-Gem Corundum
type (NGC). Later, the Macquarie GEMOC
team found that a portion of these
corundums are actually hibonites (!).
Thus, this was the first discovery of
hibonite in the SY exploration project. As
mentioned above, it should be noted
that hibonite has already been found in
southern Israel – at least mentioned in
minerals from lab analysis on specimens
there (see section 3). SY samples reach
up to few mm in size, as crystals (see
section 8 and photos below).
SY samples discussed here are taken
from (1) Kishon River Mid Reach MultiCommodity placer (alluvial samples 982,
1124, 1125, 1174, and 1175), (2)
samples 479 and 480 rock samples from
the Rakefet Magmatic Complex (RMC),
(3) eluvial sample 767 from the Muhraka
volcanic body (MHK) and (4) alluvial
sample 751 from the Migdal Ha-Emeq
area (map). While the Kishon River Mid
Reach is a narrow gap offering a
geomorphological and sedimentary trap,
the Migdal HaEmeq area is currently a
faulted block (Nazareth tilted block)
raising above the proximal reach of the
Kishon catchment. Neogene volcanics
occur along the faulted margins and
their relation to SY findings (mainly in
Mizra River) is being examined.
Hibonite occurs as rounded grains up to
few mm across, commonly with one or
more possible crystal faces. The colour
in rough tends to be purplish, but in
polished grains it commonly is
transparent and has a yellow-orange
colour similar to the Myanmar
gemstones. One characteristic feature is
the occurrence of inclusions consisting
October, 2016
9.
of native vanadium, and a typical
association with grossite (CaAl4O7) and
fluorite. The second type of occurrence
is interstitial to corundum crystals in
corundum aggregates, associated with
grossite. The SY hibonite does not
contain significant amounts of Fe or Ti.
Finally, hibonite is a common phase in
the
refractory
Calcium-Aluminum
Inclusions (CAIs) found in carbonaceous
chondrite meteorites.
As such, it
represents some of the oldest crystalline
material in the Solar system.
Conditions of Formation:
Oxygen fugacity (fO2): Hibonite is
stable over a wide range of oxygen fugacity –
as noted above, some of the metamorphic
examples contain Fe3+. In contrast, the SY
material is associated with native V, which
requires fO2 at least 8 log units more reducing
than the iron-wustite buffer. This is consistent
with the occurrence of tistarite (Ti2O3) and SiC
in the same deposits.
Temperature: Hibonite also is stable over
a range of temperature. As noted above, the
formation of hibonite in granulite-facies rocks
appears to occur at temperatures of 700-800
°C. Hibonite crystallizes from CaO-Al2O3 melts
at ca 2100 °C, through a peritectic reaction
with corundum, but in more SiO2-rich systems
the corundum-hibonite cotectic extends down
to ca 1700 °C. The presence Mg, Ti and F are
expected to lower these liquidus temperatures
further.
Pressure: There are no independent
constraints on the pressure of formation for
hibonite; it crystallized at very low pressure in
the Solar nebula, at ca 1-2 km depth in the
Hatrurim Formation, and at ca 10-30 km depth
in the granulite occurrences. The Mt Carmel
samples probably crystallized at depths
between 30 and 100 km (Griffin et al., 2016).
Page 3 from 9
Pictures of the first hibonite grains that were misidentified as corundum - sample SY-982 Kishon Mid Reach.
Top images of the hibonite mounted in epoxy, bottom left image rough grains before mounting (white scale
bar =2mm) and bottom right close up of the inclusion from 982-39.
These two grains are hibonite intergrown with grossite, fluorite, spinel (large black hexagonal crystals) and
native vanadium (small black spherical crystals). Samples: left 1175, right 982, scale bars=500m.
October, 2016
Page 4 from 9
This hibonite crystal has native vanadium in dendritic structures. Sample 1124, scale bar right=500 m
October, 2016
Page 5 from 9
October, 2016
Page 6 from 9
Shefa Yamim's hibonite findings distribution
October, 2016
Page 7 from 9
Samples of Hibonite from various sites in the world
Hibonite Mineral , Size: 0.70 x 0.73 x 0.54 cm , Weight: 0.71 g, Origin: Myanmar
Photo by kind permission of © www.gemfrance.com www.realgems.org/list_of_gemstones/hibonite.html
www.mindat.org/min-1897.html
Hibonite
Size: 0.45 x 0.43 x 0.32 cm
Weight: 0.64 ct
Origin: Mogok Area / Myanmar
Photo by kind permission of © www.americanthai.com
www.realgems.org/list_of_gemstones/hibonite.html
October, 2016
Page 8 from 9
References:
Griffin, W.L., Gain, S.E.M., Adams, D.T.,
Huang, J-X., Saunders, M., Toledo, V.,
Pearson, N.J. and O’Reilly, S.Y., 2016. First
terrestrial occurrence of tistarite (Ti2O3):
Ultra-low oxygen fugacity in the upper
mantle beneath Mt Carmel, Israel.
Geology doi:10.1130/G37910.1
Gross, S. (1977): The Mineralogy of the
Hatrurim Formation, Israel. Geological
Survey of Israel, Bulletin no. 70, 80 pp.
Ivanova, M.A., Petaev, M.I., MacPherson,
G.J., Nazarov, M.A., Taylor, L.A., Wood,
J.A., 2002. The first known natural
occurrence of calcium monoaluminate, in
a calciumaluminum-rich inclusion from the
CH chondrite Northwest Africa 470.
Meteorites & Planetary Science 37, 13371344.
Available
online
at
www.uark.edu/meteor.
Weber, D. and Bischoff, A., 1994. Grossite
(CaAI407) - a rare phase in terrestrial rocks
and meteorites. Eur. J. Mineral., 6, 591594 (SHORTNOTE).
Kolodny, Y., Burg, A, Geller, Y.I., Halicz, L.,
Zakon, Y., 2014. Veins in the combusted
metamorphic rocks, Israel; Weathering or
a retrograde event? Chemical Geology,
385, 140–155.
October, 2016
Thomas Hainschwang, Franck Notari, Laurent
Massi, Thomas Armbruster, Benjamin
Rondeau, Emmanuel Fritsch, and Mariko
Nagashima 2010. HIBONITE: A NEW GEM
MINERAL.. Gems and Gemology Summer
2010, 135-138.
Sergey I. Konovalenko, Sergey A. Ananyevb
and Sende S. Garmayeva 2012. Rare and
New Minerals
of the TashelgaMaizaskaya
Zone
of
Gornaya
Shoriya,
Their Peculiarities and Nature.
Journal of Siberian Federal University.
Engineering & Technologies 3 (2012 5)
301-310
Maaskant, P., Coolen, J.M., Burke, E.A.J.
1980. HIbonite and coexisting zoisite and
clinozoisite in a calc-silicate granulite from
southern Tanzania. Min Mag 43, 9951003.
Michel A.F. Rakotondrazafy Bernard Moine
Michel Cuney 1996. Mode of formation of
hibonite (CaAl12O19 ) within the U-Th
skarns from the granulites of S-E
Madagascar . Contrib Mineral Petrol
(1996) 123:190–201
Ulianov, A. and Kalt, A. 2006.
Mg–Al
Sapphirine- and Ca–Al Hibonite- bearing
Granulite Xenoliths from the Chyulu Hills
Volcanic Field, Kenya . Jour Petrology 47,
901-927.
Page 9 from 9