Minerals
Mohs Hardness Scale
You are probably wondering how scientists have identified over 2,000 minerals. Well, minerals have certain properties, or characteristics, that help to identify them. Minerals can be identified by their color, luster, streak, cleavage, hardness, specific gravity, and even by their chemical composition. Below you will find a table of some of these properties. |
Color
Color is not always a good clue to the identity of a mineral. Many minerals are found in several colors and many minerals have extra chemicals in them that give them an unexpected color. Also, weathering may change the color of the mineral.
Example-quartz comes in various colors: rose, milky, clear
Color is not always a good clue to the identity of a mineral. Many minerals are found in several colors and many minerals have extra chemicals in them that give them an unexpected color. Also, weathering may change the color of the mineral.
Example-quartz comes in various colors: rose, milky, clear
Luster
Luster is the way a mineral reflects light. Minerals can be described as metallic, pearly, glassy, silky, greasy, brillant, or dull. For example, diamonds are brilliant. Talc has a greasy luster, quartz has a glassy luster, and gypsum has a pearly luster. Pyrite or fool's gold, as it is sometimes called, has a metallic luster.
Luster is the way a mineral reflects light. Minerals can be described as metallic, pearly, glassy, silky, greasy, brillant, or dull. For example, diamonds are brilliant. Talc has a greasy luster, quartz has a glassy luster, and gypsum has a pearly luster. Pyrite or fool's gold, as it is sometimes called, has a metallic luster.
Streak
This is the color of the streak made by rubbing a mineral across a hard, rough surface like a bathroom tile. An example is pyrite which is brassy, yellow color. However, it makes a greenish, black steak when rubbed across a rough surface. you will need a field guide to rocks and minerals to tell you what you what color streak a mineral makes.
This is the color of the streak made by rubbing a mineral across a hard, rough surface like a bathroom tile. An example is pyrite which is brassy, yellow color. However, it makes a greenish, black steak when rubbed across a rough surface. you will need a field guide to rocks and minerals to tell you what you what color streak a mineral makes.
Cleavage
Cleavage is when certain minerals break in a definite way.
For example, galena cleaves into little cubes. Mica cleaves into thin sheets. Calcite cleaves into slanting bricks. Feldspar breaks into little steps. Quartz cleaves into irregular chunks.
Cleavage is when certain minerals break in a definite way.
For example, galena cleaves into little cubes. Mica cleaves into thin sheets. Calcite cleaves into slanting bricks. Feldspar breaks into little steps. Quartz cleaves into irregular chunks.
Hardness
Hardness is measured by seeing how easy it is to scratch a mineral.
For example, talc, the softest mineral known, can be scratched with a fingernail. Diamond, the hardest mineral, can scratch all the other minerals but cannot be scratched by them. A Germanmineralogist, Friedrich Mohs, developed a standard scale of hardness in 1822. His scale is so easy to use that it is still in use today.
Hardness is measured by seeing how easy it is to scratch a mineral.
For example, talc, the softest mineral known, can be scratched with a fingernail. Diamond, the hardest mineral, can scratch all the other minerals but cannot be scratched by them. A Germanmineralogist, Friedrich Mohs, developed a standard scale of hardness in 1822. His scale is so easy to use that it is still in use today.
Interesting Facts about Minerals
- Scientists who study minerals are called mineralogists.
- Around 99% of the minerals in the Earth's crust are made up of eight elements including oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium.
- Common minerals include quartz, feldspar, bauxite, cobalt, talc, and pyrite.
- Some minerals have a different colored streak than the color of their body.
- A gem is a piece of rare mineral such as diamond, emerald, or sapphire that is cut and polished to shine.
- Certain minerals are needed by our bodies so we can grow healthy and strong.