Mary Beth Mitchell
GEOL 113 Minerals lab
Spring 2014
Minerals
1.
Describe the following mineral properties:
Color: many minerals have a distinctive color that can be used for identification.
Although color is often a way you can identify a mineral it alone is not reliable as a
single way to identify them.
Streak: Streak is the color of the mineral in powdered form. Streak shows the true
color of the mineral. Because streak is a more accurate illustration of the mineral’s
color, streak is a more reliable property of minerals than color for identification.
Cleavage: Minerals tend to break along lines or smooth surfaces when hit sharply.
Different minerals break in different ways showing different types of cleavage.
Fracture describes the quality of the cleavage surface. Most minerals display either
uneven or grainy fracture, conchoidal (curved, shell-like lines) fracture, or hackly
(rough, jagged) fracture.
Luster: Luster is the property of minerals that indicates how much the surface of a
mineral reflects light. The luster of a mineral is affected by the brilliance of the light
used to observe the mineral surface. The most common types of lusters are metallic
and nonmetallic.
Harness: Hardness is one of the easier properties of minerals to use for identifying a
mineral. Hardness is a measure of the mineral’s resistance to scratching.. Softer
minerals can be scratched by harder minerals because the forces that hold the
crystals together are weaker and can be broken by the harder mineral
Reaction with hydrochloric acid:
hydrochloric acid is one way to quickly identify arbonate minerals and rocks. Any
rock with calcite reacts quickly with large bubbles. Reactions are very slowly, and
pure must be powdered to get even a weak reaction, very fine, slow bubbles.
Mary Beth Mitchell
GEOL 113 Minerals lab
2.
Spring 2014
How would you distinguish between the following mineral pairs:
Quartz vs. Calcite
Calcite vs. Feldspar
Quartz vs. feldspar
Augite vs. Hornblende
Biotite vs. muscovite
Hematite vs. limonite
Quartz
- contains silicon
dioxide
- hardness of 7
- does not
dissolve in acids
- weak cleavage
in 3 directions
Calcite
- rhombohedra
cleavage
- white
- good cleavage
- hardness of 3
Quartz
- consist of silicon
and oxygen
- colorless or
appears clear,
gray purple,
brown
- poor cleavage
- hardness of 7
Augite
-90 degree cleavage
-dark green
-good cleavage
Biotite
-black sheets
-good/excellent
cleavage
-2.5 / 3 hardness
Hematite
- red streak can
very in color
- poor cleavage
Calcite
-contains calcium
carbonate
-hardness of 3
-dissolves in acids
-perfect cleavage in 3
directions
Feldspar
- elongated cleavage
-more commonly
found
-contains aluminum
and silica ion
-light colored
-excellent cleavage
hardness of 6
Feldspar
more commonly found
-contains aluminum
and silica ion
-light colored
-excellent cleavage
hardness of 6
Hornblende
60- 120 degree
cleavages
-dark gray/black
- good cleavage
muscovite
-clear silvery or
coppery color sheets
-fine cleavage
-2 / 2.5 hardness
limonite
-yellow-brown streak
-submetallic
-poor cleavage
Mary Beth Mitchell
GEOL 113 Minerals lab
Spring 2014
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6 /6.5 hardness