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Minerals Notes

Types of minerals:

? Silicate Minerals - minerals that contain a combination of silicon and oxygen. They make up 90% of the Earth's crust.

? Nonsilicate Minerals - minerals that do not contain a combination of the elements silicon and oxygen. There are six classes of these elements.?

Six classes of nonsilicate minerals:

? Native elements - minerals that are composed of only one element.

? Carbonates - minerals that contain combinations of carbon and oxygen.

? Halides - compounds that are formed when atoms of the elements fluorine, chlorine, iodine, or bromine combine with sodium, potassium, or calcium.

? Oxides - compounds that are formed when an element, such as aluminum or iron, combines chemically with oxygen.

? Sulfates - contains sulfur and oxygen.

? Sulfides - minerals that contain one or more elements, such as lead, iron, or nickel, combine with sulfur.

MOH’S HARDNESS SCALE

· Hardness measures the ability of a mineral to resist scratching by another mineral or object of known hardness.

· The test used is called the Mohs' Hardness Scale.

· The scale is made up of ten minerals arranged in decreasing hardness; 1 is the softest and 10 is the hardest.

· Objects with higher value on the Mohs' scale are capable of scratching objects with lower values.

LUSTER

Either metallic or nonmetallic. Some common nonmetallic lusters are:

? Vitreous- glassy appearance

? Adamantine- diamond-like appearance

? Pearly- iridescence like pearls

? Silky- having a fibrous, silk-like luster

? Earthy- dull

CLEAVAGE

? A flat split or separation of a mineral when broken.

? Some minerals cleave in sheets and some cleave leaving flat sides.

? Some minerals have cleavage in more than one direction and others have no cleavage at all.

FRACTURE

The way a mineral breaks when it does not have cleavage. Kinds of fracture are;

? Conchoidal- bowl shaped structures like the inside of a clam shell; like obsidian

? Fibrous or splintery- fractured surface shows fibers or splinters; like asbestos

? Uneven- this surface is rough and irregular; like basalt

STREAK

? The color of powdered or crushed mineral on a piece of unglazed porcelain called a streak plate.

? The streak is much more consistent than color for the purpose of identification.

COLOR

? Metallic minerals have distinct colors.

? Nonmetallic minerals display a variety of colors.

? The use of color to identify minerals must be made cautiously because it is a subjective determination.

SPECIFIC GRAVITY

? The ratio of its weight (or mass) to the weight (or mass) of an equal volume of water.

SPECIAL PROPERTIES

? Reacts to hydrochloric acid (HCl)

may fizz when HCl applied (only fizzes after mineral is powdered)

? Is magnetic

? Changes color under an ultra-violet light

? Taste

? Smell