What is a Mineral? Identifying Minerals.

You may think that all minerals look like gems. But, in fact, most minerals look more like rocks. Does this mean that minerals are the same as rocks? Well, not really. So, what’s the difference?

For one thing, rocks are made of minerals, but minerals are not made of rocks. Mineral*: is a naturally formed, inorganic solid that has a definite crystalline structure.

The answers to the following questions will determine whether an object is a mineral: Is it a solid? Is it nonliving material? Does it have a crystalline structure? Is it formed in nature?

All minerals contain one or more of the 92 naturally occurring elements. Most minerals are made of compounds of sever different elements.

Halite is a compound of sodium, Na, and chlorine, Cl. Gold and Silver are composed of only one element. A mineral that is composed of only one element is called a native element.

Crystal*: a solid whose atoms, ions, or molecules are arranged in a definite pattern. A crystals shape is determined by the arrangement of the atoms within the crystal.

Minerals are divided into two groups based on their chemical composition. Silicate minerals Nonsilicate minerals

Silicate Minerals*: a mineral that contains a combination of silicon, oxygen, and one or more metals.

Silicate minerals make up more than 90% of the Earth’s crust.

Common Silicate Minerals Quartz: the basic building block of many rocks.

Common Silicate Minerals Mica: minerals separate easily into sheets when they break.

Common Silicate Minerals Feldspar: minerals are the main component of most rocks on the Earth’s surface.

Nonsilicate Minerals*: a mineral that does not contain compounds of silicon and oxygen.

Some of these minerals are made up of elements such as carbon, oxygen, fluorine, and sulfur. The following are the 6 classes of nonsilicate minerals.

Native elements: minerals that are composed of only one element. Ex. Copper, gold, and silver.

Carbonates: minerals that contain combinations of carbon and oxygen. Ex. Calcite, dolomite.

Halides: compounds that form when fluorine, chlorine, iodine, or bromine combine with sodium, potassium, or calcium. Ex. Halite, Fluorite.

Oxides: compounds that form when an element, such as aluminum or iron, combines chemically with oxygen. Ex. Corundum, Hematite, Magnetite

Sulfates: minerals that contain sulfur and oxygen. Ex. Gypsum

Sulfides: minerals that contain one or more elements such as lead, iron, or nickel, combined with sulfur. Ex. Pyrite, Galena, Sphalerite, Chalcanthite.

Identifying Minerals: If you closed your eyes and tasted different foods, you could probably determine what the food are by noting properties such as saltiness or sweetness. You can also determine the identity of a mineral by noting different properties.

There are 6 properties that will help to identify minerals: Color Luster Streak Cleavage and fracture Hardness Density

Color: The same mineral can come in a variety of colors. The purest form of quartz is clear, however, impurities can change the color. Because of this, color usually is not the best way to identify a mineral.

Luster*: the way in which a mineral reflects light. If a mineral is shiny, it has a metallic luster. If the mineral is dull, it luster is either submetallic or nonmetallic.

Streak*: the color of the powder of a mineral. A mineral’s streak can be found by rubbing the mineral against a piece of unglazed porcelain. The mark left is the streak. Color and streak are different.

Cleavage and Fracture: Cleavage*: the splitting of a mineral along smooth, flat surfaces. Fracture*: the manner in which a mineral breaks along either curved or irregular surfaces.

Cleavage

Fracture

Hardness: a measure of the ability of a mineral to resist scratching.

Density: ratio of the mass of a substance to the volume of the substance.

Special properties: some properties are particular to only a few types of minerals. Fluorescence Magnetism Chemical Reaction Taste Optical Properties Radioactivity