Download Name

Name: _______________________________________
class: ___________ date: ___________
Mineral Identification
Problem: Can we identify unknown minerals by their properties?
Background: Although nearly 2500 minerals are know to occur within Earth's crust, most are
rare, with only about 100 occurring in abundance. Of those 100 minerals, 15 make up the
common rock-forming minerals. You cannot always identify a mineral by its appearance.
Sometimes multiple samples of the same mineral can look very different. For example, calcite
can be clear, white, gray, yellow, or other colors. Many metals are black. Scientists use other
properties of minerals to identify them. They often use a classification scheme, starting with
luster, to arrive at an identification.
Procedure: Use the ESRT, the text book and your knowledge of minerals’ properties to
identify the samples, progressing through a series of questions, starting with luster.
Luster: Some minerals clearly reflect light like a metal; some metals are not reflective, are
dull, yet something about it appears to be metallic. Is the mineral Metallic or non-metallic?
Hardness: Use simple hardness tools - penny and glass plate. Determine a hardness range: Is
the sample less than 3 (does not scratch a penny)? Is the sample less than 5.5 (doesn’t scratch
glass)? Is the sample greater than 6 (scratches glass)?
Cleavage / fracture: If you look closely at minerals you may see that they appear to have
sharp, straight edges & smooth, flat surfaces. It may seem as if the crystal has been polished
on some surfaces. A mineral may break at specific angles. This indicates cleavage. Cleavage
can occur in one, two, three, or four directions. Some minerals may not show their cleavage if
they’ve been weathered, especially if it is a soft mineral. Graphite should show cleavage but is
soft and people rub the edges, removing any trace of cleavage.
Breakage that is curved or irregular is called fracture.
Does the sample show cleavage or fracture?
Streak: Rub the mineral once along an unglazed tile. The color of a mineral when it is
powdered is often more diagnostic than the color in the natural sample. Minerals that are
harder than the tile will not usually leave a streak.
Is the streak light colored or is the streak dark or is there no streak?
Special characteristics: Some minerals have special exclusive characteristics. Calcite and
dolomite are alkaline and will react chemically to an acid by bubbling. Transparent calcite will
exhibit double refraction if placed on printed words. Magnetite attracts magnets. Talc and
graphite have a greasy feel. Quartz shows concoidal fracture. Some minerals respond to UV
light by glowing different colors in the dark. Sulfur smells like rotten eggs.
Name
Class
Group
date
Hypothesis: If I make observations of minerals’ properties, then _____________________________________
__________________________________________________________________________________________
Because ___________________________________________________________________________________
Procedure: Use the ESRT, the text book and your knowledge of minerals’ properties to identify the samples,
progressing through a series of questions, starting with luster:
Determine the sample minerals’ characteristics. Use the answers to arrive at an identification:
Luster
Cleavage/
Hardness:
Streak:
Special
Mineral
(metallic or
fracture
1-3
Light color; characteristic
Identification
Sample
nonmetallic)
4-5
Dark color;
6-10
no streak
Analysis and Conclusion:
Were you able to identify the mineral samples? __________
Explain how the minerals’ properties helped you identify them. Give 3 specific examples. _______________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________