Rocks and Minerals

Rocks and Minerals Rocks: naturally occurring combination of minerals Minerals: natural, solid substance that has definite chemical composition and physical structure. All rocks contain minerals. The building block of rocks

Mineral Property Minerals can be identified by looking at its properties or physical and chemical characteristics 7 ways + 2 special ways

7 ways to identify minerals/rocks Color Streak Luster Cleavage Fracture Density Hardness

2 Special ways to Identify minerals/rocks Acid base test UV light test

Color The color of a mineral sample. Different samples of the same mineral may have more than one color

Streak The color of the powder of the mineral. Minerals are scraped across a streak plate, Minerals may look similar, but have a different streak

Luster The way light reflects from the mineral’s surface. May be metallic or nonmetallic (glassy is nonmetallic) May vary from sample to sample

Metallic Luster Non metallic luster

Minerals break The way a mineral breaks is often a better clue as to its identity Bonds between atoms may be equal in all directions or they may be stronger within layers

Cleavage The tendency of a mineral to break along flat surfaces Minerals will have flat surfaces, may be in 2 or more directions

Halite, breaks in 90 degree angles

Fracture The tendency of a mineral to break into irregular, jagged pieces. Atomic bonds are fairly equal in all directions

Fracture

Density Amount of mass in a given volume of a mineral 2 minerals may appear the same but one may be much lighter

Hardness A mineral’s resistance to being scratched. Determined by the strength between atoms.

Mohs Scale Describes a mineral’s hardness. Talc = 1– baby powder Diamond is the hardest mineral = 10 the only thing that can scratch a diamond is another diamond

Mohls Scale

Acid test: React with acid = carbonate minerals (bubbles) Special Properties Acid test: React with acid = carbonate minerals (bubbles) Fluorescence = minerals glow when exposed to UV light

Standard Light UV light

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