Minerals

Rock vs. Mineral Mineral Naturally occurring – not made by man Inorganic – does not come from materials that were once living Solid – has a definite volume and shape Crystal Structure – the particles of the mineral line up in a pattern. Has a definite chemical composition Rock Made up of two or more minerals and can contain organic materials.

Minerals are Important

Identifying Minerals Hardness Luster Crystal shape Streak Color Fracture and cleavage Density

Mineral Identification Hardness - how hard is it? (what can you scratch it with and what will it scratch?) See page F122 Mohs Hardness Scale

Mineral Identification Luster (how a mineral reflects light)

Luster (continued) Some terms used to describe luster are: shiny, metallic, glassy, earthy, waxy, pearly, silky Pyrite -metallic Unknown - earthy Unknown - silky

Mineral Identification Crystal Shape (what shape is the crystal?)

Mineral Identification Streak (does it leave a colored line behind when rubbed across a surface?)

Mineral Identification Color – some minerals are always one color, some can be many colors Calcite – found in many colors Azurite – blue

Mineral Identification Cleavage and Fracture (how a mineral breaks apart) Cleavage – splits along a flat surface Fracture – irregular break

Density – each mineral has a characteristic density No matter the size or shape of the mineral, it will have the same density Density = mass/volume Mineral Identification

Galena Galena is a valuable ore for lead, since lead doesn't occur naturally alone. Because galena is made mostly of lead, it is very heavy for its size.

Pyrite Pyrite is a very important iron ore mineral. Many early prospectors mistook it for gold, hence the nickname, Fools' Gold.

Magnetite Magnetite is another iron ore. Iron molecules line up north and south while in the liquid state making a natural magnet.

Sulfur Sulfur occurs as an element. Man uses it in a variety of ways and it has a very distinct rotten egg smell.

Calcite Calcite is found in nature in caves, seashells, eggshells and bones. Acid will make it bubble.

Quartz Quartz is found in a lot of the rocks in Earth's crust. People also like it to make jewelry.

Muscovite Muscovite comes in light-colored paper-like sheets. Early settlers used large sheets as windows in their homes.

Hematite Hematite is an iron ore mineral. It has a distinctive red streak (even though the mineral sometimes is black!) You have probably seen it as metallic black jewelry.

Talc Talc is a familiar mineral, best know for being talcum powder (baby powder.)

Hornblende Hornblende is a very dark, fibrous mineral found in many rocks.

Feldspar Feldspar is the largest rock forming mineral. It is found in a variety of colors.

Graphite Graphite is made of the same element as diamonds, but it is really soft. It is used as a dry lubricant and also as the "lead" in your pencil.

THE BOTTOM LINE: Rocks are Made of Minerals