Minerals

Definition: A mineral is naturally occurring Made by Mother Nature -it is NOT man made!

An inorganic material (It is NOT and has NEVER been living)

It is NOT a liquid It is NOT a gas It is a SOLID

It has a crystalline structure when examined under a microscope It has either a cubic hexagonal orthorhombic monoclinic triclinic or tetragonal Crystalline Structure

It has a definite chemical composition Every atom of the mineral has the same chemical formula For example: Halite: NaCl Galena: PbS Fluorite: CaF 2 Talc: Mg 3 Si 4 O 10 (OH) 2

A mineral is: naturally occurring inorganic solid crystalline structure chemical composition Now I See Crystal Clear.

Classification of minerals HARDNESS Geologists use the Mohs Hardness Scale to determine a mineral’s hardness. The Mohs Hardness Scale ranks a mineral’s hardness from 1-10 with 1 being the softest ( can scratch it with your fingernail) and 10 being the hardest (cannot be scratched by any other substance). The mineral with a Mohs Hardness Scale of 1 is talc. The mineral with a Mohs Hardness Scale of 10 is diamond.

Color Color is a physical property of a mineral. It is NOT a dependable way to classify minerals because many minerals may have the same color. Examples: Gold and pyrite are both gold. Quartz may be rosy pink, white, purple, gray or yellowy.

Streak A mineral’s streak is the color it leaves behind when scratched on an unglazed tile called a streak plate. A mineral’s streak is the color of its powder.

Luster A mineral’s luster describes how the mineral reflects light. Examples: Minerals that are metals are shiny. Quartz has a glassy luster. Talc has a greasy luster.

Density Each mineral has its own characteristic density. That is why density is an excellent way to identify a mineral. Density refers to a mineral’s mass per unit of volume. Geologists use a balance to determine a mineral’s mass and water displacement with a graduated cylinder to determine its volume. Density is expressed in units called grams per cubic centimeter. The formula for calculating the density of a mineral (or any substance) is its mass divided by its volume.

Cleavage and Fracture Cleavage refers to a mineral’s ability to split along flat surfaces. (String cheese has cleavage along a regular surface.) Fracture refers to a mineral’s ability to break along irregular surfaces. (Tearing a piece of paper is an example of what this looks like.)

Special Properties Some minerals have magnetic properties. That means that they are attracted to magnets. Some minerals are fluorescent. That means that they glow under ultra violet (UV) light. Some minerals are radioactive. They cause a Geiger counter to be set off. Other minerals have electrical properties. Quartz produces a slight electrical current when pressure is applied to it.