Aim Aim: What are the characteristics of minerals and how do we identify them? Minerals I. Minerals A. 4 Characteristics 1. Naturally occurring 2. solid materials 3. atoms are arranged in an orderly manner 4. inorganic 5. have a definite chemical composition “NSAID”

Rock forming minerals B. Rock forming minerals – of the 2400 minerals on the earth, about a dozen of them are so abundant that they comprise of more than 90% of the lithosphere. 1. Lithosphere – outer shell of the earth consisting of the crust and uppermost part of mantle.

C. Elements in minerals – mineral’s may be composed of single elements or compounds of two or more elements. 1.Most common elements in minerals: a. Oxygen (O) – since it is the most abundant element in earth’s crust by both mass (46.6%) and volume (93.8%). b. Silicon (Si) – 27.7% by mass and 0.9% by volume. c. Aluminum (Al)d. Iron (Fe) e. Calcium (Ca)f. Sodium (Na) g. Potassium (K)h. Magnesium (Mg)

Silica Tetrahedron SiO 4 – 4 oxygen atoms to every silicon atom animation

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1.Color 1.Color – may be used for mineral identification. Many minerals have the same color. It is NOT the most reliable method of identifying a mineral. Different minerals with the same color

2 Different types of quartz – same mineral, different color.

Hardness 2. Hardness - the resistance of a mineral to being scratched. If you scratch two minerals together, the harder mineral will scratch the softer one. a. Mohs’ Scale of Hardness Hardness - assigns a value of 1 through 10 to a mineral, with “1” being the softest value (talc) and “10” being the hardest value (diamond).

Streak 3. Streak – the color of the powder of a mineral when crushed or scratched across a streak plate (piece of unglazed porcelain). A mineral’s color may look different than its streak. Generally, nonmetallic minerals do not leave a streak.

What are three ways that we can identify minerals?

Luster 4. Luster – the appearance of light reflected from a minerals’ surface. Metallic luster a. Metallic luster – shines like a metal nonmetallic luster b. nonmetallic luster – might look glassy, waxy, greasy, pearly, earthy, or dull. Pyrite (Fools Gold) metallic Nonmetallic

Cleavage 5. Cleavage – when a mineral breaks along one or more smooth surfaces galena

Fracture Fracture a. Fracture – when minerals do not break along flat planes.

Crystal Structure 6. Crystal Structure – a crystal is a regular shaped solid formed by an ordered pattern of atoms. Minerals have characteristic crystals. (Pyrite – calcite)

Density 7. Density Specific gravity a. Specific gravity – Weight of a mineral divided by weight of an equal volume of water.

C 3 S 2 HL