What is a mineral?
A mineral is a chemical element or compound that is naturally occuring and has a crystal structure. A mineral resource is a rock or mineral that can be mined and used for specific purpose. Precious minerals like gems are polished to make jewlery. There are about 4000 minerals, and some of them look alike.
The clues to minerals and rocks.
There are several important clues to know which mineral is which. Including, crystal structure, hardness, lustre, color, streak, and fracture.
mohs hardness scale.
Hardness is a measure of the mineral's resistance to being scratched.
How can hardness be used to indentify minerals? German scientist Friedrich Mohs asked himself that question in 1812. He developed a scale of ten minerals with a hardness value of 1 to 10. The higher the number on the Mohs hardness scale, the harder the mineral.
How can hardness be used to indentify minerals? German scientist Friedrich Mohs asked himself that question in 1812. He developed a scale of ten minerals with a hardness value of 1 to 10. The higher the number on the Mohs hardness scale, the harder the mineral.
shine and lustre.
Some minerals, such as gold and silver, appear shiny (another clue to their identity). Other minerals appear dull. The shininess, or lustre, of a mineral depends on how light is reflected from its surface. If a mineral shines like a polised metal surface, it is said to have a metallic lustre. If a mineral does not shine like a mineral is has a non-metallic lustre.
color
Color is one of the most attractive properties of a mineral. The color of a mineral can also be a clue to its identity. However, color alone cannot identify a mineral. Two or more minerals can have the same color. Also one mineral can be found in several different colors. Corundum (made of aluminum and oxygen) is white when pure.
streak
When a mineral is rubbed across a piece of unglazed porcelain tile, it leaves a streak. The porcelain tile has a hardness value of 7 so if the mineral leaves a streak on the tile, it has a hardness value of less than 7. If the mineral does not leave a streak on the tile it has a hardness value of more than 7. The mineral that is used in pencils is graphite. Pencil marks are graphite streaks that are soft enough to be left on a piece of paper. One way to identify whether a mineral is gold or pyrite is to use a streak test. Gold would leave a golden streak and pyrite would leave a greenish-black or brownish-black streak.
cleavage and fracture
Another clue to a minerals identity is the way it breaks apart. If a mineral breaks along planes, (smooth, flat surfaces) it is most likely to have cleavage. An example of a mineral with cleavage is mica. Separating the layers of mica is like separating the pages in a book. Although, not all minerals have cleavage. Fracture is when minerals breaks with rough of jagged edges. An example of a mineral with fracture is quartz. You need to look at a freshly broken surface of a mineral to examine if it has cleavage of fracture.