Get it???
It’s a polymorph
Today
• Part III- Minerals
PP
• Lab # 2- mineral
identification
Next Tuesday
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No quiz
The rock cycle PP
Salt crystal ACT
Rock types ACT
Part III. Physical properties of minerals
Quartz and Calcite –
Many colors
Color
Malachite – Always green
Azurite – Always green
Hematite – Red-brown streak
Streak- color of the powder provided by pulverizing the
mineral
Gypsum – Satiny luster
Quartz – Vitreous luster
Pyrite –Metallic luster
Talc –Pearly luster
Luster-a description of the way light interacts with the surface of
a crystal, rock or mineral- Metallic or nonmetallic?
Hardness
Plagioclase/K-feldspar
Galena
Specific Gravity- aka density(D= mass/vol)
Cubes
Dodecahedra
Octahedra
Compound Forms
Blades
Rhombohedra
Hexagonal Prisms
Tetragonal Prisms
Crystal Habit- shape of a single or group of minerals
(blocky, columnar, needle-like, bladed, equant)
Euhedral-well formed faces
Anhedral- faces are squished together and not
well defined
Cleavage and Fracture
Cleavage- tendency for a mineral to break along the direction
of its weakest bonds (cleavage planes)
Differs from crystal habit
Fracture- breaking in an irregular or conchoidal way
Mica
Cleavage
Plagioclase
Hornblende
Cleavage
Halite
Calcite
Conchoidal
Fracture
Cleavage is
different from
crystal habit
Cleavage can be
repeated, a
crystal face is one
surface
• Ask yourself: “If I smashed it with a hammer,
would it shatter or break into organized pieces?”