Minerals are natural inorganic (non-living) substances that have the same chemical makeup and crystal shape. A mineral's color depends on what's mixed in with it. Some minerals have metal with a metallic luster (how it reflects light) mixed in with them that causes them to shine. Minerals that don't contain metals look dull.
	Most times when we think of minerals we think of a powder. But minerals can be as hard or harder than the things we think of as rocks. Diamonds for example are extremely hard.
	We can use tools to check for hardness of minerals and rocks. For example, a glass plate (H=5.5), an unglazed porcelain streak plate (H=7.5), and a nail or pocket knife (H=5.0) can be used. If we have a mineral that has a harness of 6 it will scratch the glass plate and the nail but NOT the streak plate. Another way to determine hardness is to scratch minerals on each other. The one that leaves the mark is the HARDER mineral or rock.
	The Mohs Hardness Scale is a relative scale. This means that a mineral will scratch any substance lower on the scale and will be scratched by any substance with a higher number.

Streak plates can also help us identify a mineral. The color of the powder left behind on the streak plate is the mineral's streak. The streak and color of some minerals are the same. For others, the streak may be quite different from the color, as for example the red-brown streak of hematite, often a gray to silver-gray mineral. Also, not all rocks and minerals leave a streak (because they are softer than the plate). The combination of luster, color, and streak may be enough to help us identify minerals.

Examples of STREAK: