Minerals

Characteristics of minerals Naturally forming Solid Has a definite chemical makeup Has a crystal structure Inorganic

How are minerals grouped Based on their chemical makeup Silicates most common o Contain oxygen and silicon o Make up 90% of the rocks in Earth’s crust o Quartz o Feldspar o Mica

How are minerals grouped continued Carbonates o Another group common in rocks o Contain carbon and oxygen o React with HCL (Hydrochloric Acid) o Calcite Oxides o Do not form rocks o From where most metals are refined from o When an element (metal) joins with oxygen

Properties to help identify a mineral 1.Color a.Three factors that determine color Tiny amounts of an element that is not part of the normal chemical makeup o Pure Quartz is clear and colorless but tiny amounts of iron make it violet – Called amethyst Can change when it is at or near Earth’s surface verses in contact with the atmosphere or water May have defects in their crystal structure that change the color

Properties to help identify a mineral 2.Streak a.Color of the powder left behind when the mineral is scraped across a surface b.Streak plates used to determine the color c.Better clue to the identity than surface color d.All samples of the same mineral will have the same streak color

Properties to help identify a mineral 3.Luster a.The way light reflects from its surface b.Metallic Looks like it was made of metal c.Nonmetallic Does not look like its made of metal d.Can very from sample to sample – just like color e.If the mineral is broken it will reveal its characteristic luster

Properties to help identify a mineral 4.Cleavage a.The tendency of a mineral to break along flat surfaces b.Depends on how the atoms are bonded together Crystal structure is weaker in the direction in which the mineral breaks c.Both the direction and smoothness of the broken surface are considered

Properties to help identify a mineral 5.Fracture a.Tendency of a mineral to break into irregular pieces b.Bonds that join the atoms are fairly equal in strength in all directions

Properties to help identify a mineral 6.Density a.Very helpful in identifying the mineral b.Every mineral has its own density no matter what the sample size is

Properties to help identify a mineral 7.Hardness a.The resistance to being scratched b.Mohs Scale c.Minerals can scratch another mineral of the same hardness or softer

Some special properties of minerals Carbonic minerals react with hydrochloric acid Fluorescence o Glow when exposed to ultraviolet light o Fluorite &calcite o Not very helpful o Some samples of the same element might or might not have the property

Some special properties of minerals Magnetic o Magnets are pulled toward the mineral o Magnetite is strongly magnetic Radioactive o Contain unstable elements that change into other elements over time o This releases energy This energy is measured to identify the mineral Uraninite, Autunite, Uranopilite, and Andersonite