What is this? Are you sure this is a rock? What else could it be? What tests could you do to determine the type of rock you just picked up?
3-1 Properties of Minerals What is a Mineral? Identifying Minerals
What is a mineral? To be a mineral a substance must have the following characteristics: Inorganic Solid Naturally Occurring Has a Crystal structure Definite chemical composition
Inorganic A mineral cannot form from materials that were once part of living things.
Solid Minerals are solid, which means they have a definite volume and shape. The particles in a solid are tightly packed together so they cannot move.
Minerals are solid.
Naturally Occurring Formed by processes in nature
Crystal Structure The particles in a mineral form a repeating pattern
Definite Chemical Composition A mineral always contains certain elements in certain amounts. Example: SiO2 is Quartz
Color Color can be used to identify a few minerals This is not the best test because many minerals are the same color.
Streak The streak test identifies the color of the powder of a mineral. While a mineral’s color may change its streak will not.
Luster Luster refers to the way that light reflects off of the mineral’s surface.
Density Density is defined as “Mass per unit volume.” In other words, how many particles are in a certain area.
Hardness Hardness is a minerals characteristic of being able to scratch softer minerals and be scratched by harder minerals
Moh’s Hardness Scale Moh’s Hardness scale Ranks minerals from softest (1) to hardest (10)
Crystal Systems Each mineral has a particular crystal structure Example Cubic, hexogonal
Crystal Structure
Cleavage and Fracture Minerals with cleavage break along flat plains. While minerals with fracture break more jaggedly but the break can still have a pattern. For example: the image above has fracture in a sea-shell shape.
Fracture
Cleavage
Special Properties Some minerals can be identified by special properties they have. For example: Magnetite is magnetic and Scheelite glows in the dark (fluorescence )