Mineral Identification
Objectives- How are minerals identified
In order to identify a mineral, several tests are needed. With over 3,000 minerals, it would be
impossible to find one test that could be used to identify all of them. For example, one property that
can be used is color. However, many minerals have the same color and some minerals have several
colors. Hopefully, you can see why multiple tests are needed. After doing several tests, a mineral can
be identified by using its unique set of properties. Most of the tests test for physical properties. Physical
properties are properties that can be measured or observed.
A good test to use to test hardness is Mohs Hardness Scale. The scale goes from one to ten,
with ten being the hardest. A diamond has a hardness of ten and talc has a hardness of one. One way of
testing hardness is seeing if one mineral will scratch another. If it will, then it is harder than it. The
other way to test hardness is to see if the mineral will scratch an object such as glass (hardness of 6.5) or
your fingernail (hardness of 2.5).
Another test to use is streak. Streak is the color of the powdered mineral. Regardless of the
color a mineral has, a mineral will only have one color of streak.
Luster is the ability of a mineral to reflect light. Generally luster is broken down into two
categories, metallic (like a metal) and nonmetallic. Other categories of luster may include earthy, glassy,
waxy or pearly.
The crystal system or arrangement of the atoms can be useful if it is obvious. Quartz has a six
sided or hexagonal arrangement, halite is cubic and mica is flat like a sheet of paper.
The way a mineral breaks can be used. If a mineral breaks along smooth flat surfaces, it has
cleavage. A mineral has fracture if it breaks along rough or jagged edges. Categories of fracture include
earthy and hacky.
Density, or heavy something is for its size, is very helpful. When atoms are backed very tightly
together, it produces a high density. To determine the density, use the formula D = m/v. The label for
density is usually g/mL. Regardless of the size of specimen, a particular type of mineral will only have
one density.
Other special properties include taste (halite taste salty), being magnetic (magnetite), bend light
in special ways (calcite) or glow colors under an ultraviolet light (fluorescence).
Sometimes chemical properties can be used. Chemical properties are ones that explain how a
mineral will react. One of the better ones is to drip HCl (hydrochloric acid) on the mineral. Some
minerals will bubbly when the acid is placed on it. Those minerals contain the compound calcium
carbonate.
Questions:
1. T/F Each mineral has its own specific properties.
2. The softest known mineral is ______________ and the hardest one is _________________.
3. T/F A mineral can scratch any mineral harder than itself.
4. Why can’t color alone be used to identify most minerals?
5. The color of a mineral’s powder is it’s _________________.
6. The term that describes how a mineral reflects light from its surface is ______________________.
7. Circle the letter of each sentence that is true about the density of a mineral
a. A given mineral can have varying densities.
b. The larger the sample of a mineral, the greater its density.
c. Each mineral has a characteristic density.
d. The density of a mineral is its mass divided by its volume.
8. T/F Each pieces of a mineral has the same crystal structure.
Matching
9. _____ cleavage
a. A mineral’s ability to split easily along flat surfaces
10. _____ fracture
b. A mineral’s ability to glow under ultraviolet light
11. _____ fluorescence c. A mineral’s ability to break along rough edges.