Minerals and Mineral Properties

What is a Mineral? Naturally-Occurring Inorganic Solid Crystal Structure Defined Chemical Composition

What is a Mineral? A mineral MUST have all five characteristics in order to be considered a mineral. If not, it is NOT a mineral.

Naturally Occurring Means the substance must be formed by processes that occur in the natural world. Example: Magma cooling to form Quartz

Inorganic Can’t form from materials that were once part of living things. Can’t come from plants, trees, or animals. Example: Coal comes from remains of plants. Therefore, coal is NOT a mineral.

Solid A mineral is always a solid, with a definite volume and shape.

Crystal Structure Particles must line up in a pattern that repeats over and over again. Repeating pattern that forms a solid is called a crystal.

Definite chemical composition Meaning that a mineral always contains certain elements. Example: Diamond is nothing but carbon atoms. Example: Graphite is nothing but carbon atoms.

Identifying Minerals Color Hardness Streak Color Crystal Structure Luster Density Hardness Crystal Structure Cleavage/Fracture Special Properties

Color Color is an observation based on the color of the minerals. Gold Pyrite Chalcopyrite

Streak Color Color of the mineral’s powder. Observed by rubbing mineral against a streak plate. ***STREAK COLOR AND MINERAL COLOR CAN BE DIFFERENT***

Luster Describes how light is reflected from a mineral’s surface. 6 different types of luster, we only care about 2: Metallic & Nonmetallic(Dull, Glassy, Silky, Waxy (Greasy/Pearly), Earthy)

MEtallic Luster Pyrite has a metallic luster. Bright, shiny. Looks like a metal.

dull luster Graphite has a dull luster. Not shiny, dull in color. Hard to describe just by looking at it.

Glassy luster Looks kind of like glass. Quartz has a glassy luster. Topaz has a glassy luster.

silky luster Looks and feels sort of silky. Does not necessarily feel like a mineral. Malachite has a silky luster.

Waxy(Greasy/Pearly) Luster Talc has a waxy luster. Waxy luster kind of feels like and looks like a candle. This is where the waxy luster comes from.

Earthy Luster Looks kind of like a rock. Hematite has an earthy luster.

Density Each mineral has a specific density. No matter the size of the mineral, the density remains the same. Density = mass ÷ volume

Hardness 1812, Friedrich Mohs, invented the Mohs Hardness Scale Used to test hardness of minerals. Hardness determined by a scratch test.

Crystal Structure All minerals have ONE of six crystal structures. Minerals are grouped based on the type of crystal structure they have.

Cleavage Splits easily along a flat surface. Calcite is a good example of cleavage in minerals!

Fracture Unlike cleavage, fracture describes how minerals break apart in an irregular way.

Special Properties Magnetic? Reacts with acid? Fluorescence? Some minerals have these special properties!