TABLE FOR MINERAL IDENTIFICATION – LAB #4
Mohs
Hardness
Luster
Color
Streak
Crystal Form/
Structure
Cleavage &
Fracture
Misc. Properties
2-3
Pearly to
vitreous
Black or dark
brown
Light
gray or
brown
Platy, sheet-like,
flaky
One perfect
cleavage
Elastic; hardness
varies with direction
2-3
Pearly to
vitreous
Silver-white,
brownishwhite; pale
green
white
Platy, sheet-like,
flaky
One perfect
cleavage
Transparent; elastic;
hardness varies with
direction
Resinous or
dull
Black, brown
or dark green
Greenish
gray
Blocky, tabular
2 cleavages at
90º (prismatic);
Opaque in hand
specimen
5-6.5
uneven fracture
on third plane.
5-6
Vitreous to
dull
Black or dark
green
Pale gray
to white
Columnar or
prismatic
cleavage
fragment.
Elongated
crystals grown
together in
massive form
5.5-6.5
Vitreous to
pearly on
cleavage
surfaces;
Waxy to dull
on fracture
surfaces
Colorless,
white, pink,
gray, etc
White
2 oblique
cleavages;
2 cleavages at
90º; uneven
Cleavage
fragment
fracture on third
plane
BIOTITE
K(Fe) phyllosilicate
MUSCOVITE
KAl phyllosilicate
AUGITE
Ca (Mg,Fe) pyroxene
Opaque in hand
specimen
HORNBLENDE
May contain perthite:
an intergrowth of two
feldspars
compositions (Na and
K).
ORTHOCLASE
uneven fracture
on third plane
Elongate or
tabular prisms;
Name/Chem.
Formula
Results in a woody or
veiny appearance.
Ca(Mg, Fe, Al)
amphibole
KAlSi3O8
TABLE FOR MINERAL IDENTIFICATION – LAB #4
Mohs
Hardness
5.5-6.5
Luster
Color
Streak
Vitreous to
pearly on
cleavage
surfaces;
Colorless,
white, gray,
etc
white
Waxy to dull
on fracture
surfaces
6.5-7
7
Vitreous
Vitreous
Yellow to
yellow-green
White
Colorless,
white, gray,
etc
White
Crystal Form/
Structure
Cleavage &
Fracture
Elongate or
tabular prisms;
2 cleavages at
90º; uneven
Cleavage
fragment
fracture on third
plane
Massive to
Granular
Conchoidal
fracture
translucent
Hexagonal
prisms;
Conchoidal
fracture
Striations on crystal
faces
May be granular
to massive.
Misc. Properties
Twinning striations
on one cleavage
parallel to the second
cleavage.
Name/Chem.
Formula
PLAGIOCLASE
(Na,Ca)(Si,Al)4O8
Perfectly parallel
lines.
OLIVINE
(Mg, Fe)2SiO4
QUARTZ
SiO2
Var. crystal (clear);
smoky; rose; milky;
amethyst (purple)