Minerals are chemical elements or compounds that form a rock. There are many minerals in the world. There are so many that some minerals end up looking like each other! Geologists, Scientists who study rocks and minerals, use different tests to identify each mineral. These tests are: Hardness, Crystal Structure, Lustre, Colour, Streak, and Cleavage/Fracture.
Hardness is a mineral test involving Moh's Hardness Scale. The hardness scale measures a minerals resistance to scratching from 1-10, 1 being the softest and 10 being the hardest. Talc is one of the softest materials in the world, its so soft you can scratch it with your fingernail. Diamond is the hardest, only able to be scratched by diamond itself.
There are 7 Major Crystal Systems in the world. Crystal systems tell us about the shape of a mineral. The 7 systems are: Cubic, Tetragonal, Orthorhombic, Monoclinic, Triclinic, Hexagonal, and Trigonal. Cubic is in the shape of a cube, Tetragonal is a rectangle, Orthorhombic is a smaller type of rectangle, Monoclinic is even smaller, Triclinic is the smallest rectangle, Hexagonal is in the shape of a hexagon and Trigonal is a mix between a cubic and hexagonal shape.
Lustre is a minerals shine. A minerals shine is put into to groups of lustre. Metallic lustre is where a mineral shines like polished metal and Non Metallic lustre is where a mineral does not shine like polished metal. Some examples of non metallic lustre are Waxy: where the mineral feels like wax, Pearly: where the mineral looks like pearl, Silky: where the mineral has a shine like silk, Greasy: it looks as if its covered in oil, Glassy: it has a reflection like glass, and Adamantine: the mineral shines like a diamond.
Color is probably one of the least important mineral tests because there are so many minerals they all look the same! Color, although not very useful, tells us a minerals colour.
The streak of a mineral is the mark it will leave on an unglazed porcelain tile. The streak will help us identify different minerals because some minerals leave no streak, some leave a white streak and some will leave a coloured streak.
Cleavage And Fracture
_Cleavage and Fracture is the test that tells us how a mineral breaks. If a mineral has cleavage it will break in nice smooth edges. If it has fracture then the mineral will break in rough jagged edges. An example of a mineral with cleavage is Mica (My-KA). This mineral breaks in smooth flat planes. An example of fracture is quartz. This mineral breaks in rough jagged edges.