2.4-2.5 Notes
How do we identify minerals?
The characteristics of an object that can be observed or measured are its physical
properties. Some physical properties of minerals are color, streak, luster, and
hardness.
Color- Some minerals cannot be identified by color alone, because many minerals
are the same color. For example, gold and pyrite are both brassy yellow. Other
minerals are found in more than one color. For example, Quartz can be found in
many colors, such as pink, purple, yellow, or colorless. Two minerals found only
in a single color are malachite (green) and azurite (blue).
Streak is the color of the
powder left by a mineral.
You can find the streak of a
mineral by rubbing it across
a square unglazed ceramic
tile. A mineral can be found
in many different colors.
However, its streak is
ALWAYS the same.
Luster refers to the way a mineral’s surface reflects light. Luster is either metallic
or non-metallic. Minerals with a metallic luster shine a new coin. Non-metallic
lusters are generally referred to as waxy, glassy, or dull.
Hardness is the property of a mineral
that relates to how much it resists being
scratched. The Moh’s scale ranks ten
minerals in hardness from 1-10. The
higher the number, the harder the
mineral. For example, a mineral with a
hardness of 10 can scratch any mineral
that has a lower number.
All matter has mass and volume. Density is the amount of matter in a given
volume. The density of a mineral NEVER changes. It is measured in grams per
cubic centimeters, or g/cm3
The formula is:
Density=Mass/Volume
For example, suppose you have a sample of talc that has a mass of 26g and a
volume of 10 cm3. If you divide 26g by 10cm3, you will get a density of 2.6 g/cm3.
Magnetism is a force of attraction or
repulsion shown by matter that is
magnetic. Objects made of iron, nickel,
cobalt, or steel are attracted to a magnet.
Magnetite also shows the property of
magnetism.
The acid test helps identify minerals that contain calcium carbonate. You place a
drop of diluted acid on a small piece of the mineral. If the surface of the mineral
fizzes, the mineral contains calcium carbonate.