Properties of Minerals

Science, Grade 6


Table Of Contents: Properties of Minerals

1. How Are Minerals Identified?
Minerals are identified by their physical properties. There are a number of properties that can be tested.
2. Mineral Hardness
A mineral's hardness is determined by comparing it to the minerals in the Mohs Hardness Scale. For example, halite is harder than gypsum because it will scratch gypsum. But, when halite is rubbed against calcite, it gets scratched. That means halite has a hardness between 2 and 3.
3. Mineral Color
The color of a mineral is easy to see but is not always the best way to identify it. Many minerals are the same color, and some minerals can change color if they are exposed to different conditions, like air or water.
4. Mineral Streak Color
Streak is the color of a mineral when it is crushed to a powder. If you rub a mineral across a piece of unglazed porcelain, a streak is seen. Minerals harder than a 7 on the Mohs Hardness Scale do not leave a streak.
5. Mineral Luster
Luster is a description of how light reflects off of a mineral. Some of the luster descriptions are metallic, glassy, greasy and dull.
6. Specific Gravity of a Mineral
Specific gravity is a measure of a mineral's density. Density is determined by comparing the mass of a mineral to the mass of an equal volume of water. Volume is measured by dropping a mineral sample in water and looking at the amount of displacement. A scale is used to measure mass.
7. Mineral Crystal System
Every mineral forms a specific crystal shape and belongs to one of several different crystal systems. Each system is determined by the internal arrangement of the molecules in a mineral.
8. Cleavage or Fracture of a Mineral
A mineral that breaks apart in flat planes has cleavage. A mineral that breaks unevenly along irregular surfaces has fracture. There are several different types of fracture.
9. Mineral Special Properties
Some minerals have unique physical properties. For example, calcite glows under ultraviolet light, and magnetite is magnetic.
10. Mineral Properties Table
If you have a sample of an unknown mineral, you can use all of these physical properties to identify it.