Chapter 3:Minerals of the Earth’s Crust Mineral-A naturally formed inorganic solid that has a definite crystalline structure. Rocks are composed of minerals. Contain one or more of 92 elements. Element-A pure substance that cannot be broken down into a simpler substance. Native Element -A mineral that is composed of only one element. Compound-A substance composed of two or more elements that have been chemically combined.

Minerals are classified by their chemical composition 1.Silicate Minerals -minerals composed of silicon, oxygen and other elements and make up 90% of the Earth’s crust. 2.Nonsilicate Minerals -minerals that do not contain silicon and oxygen. a. Carbonates: contain carbon and oxygen. b. Sulfides: contain one or more elements combined with sulphur. c. Sulfates: contain sulphur and oxygen in the form of SO4. d. Native Elements e. Oxides: Contains elements combined with oxygen. f. Halides: Compounds such as salt (NaCl) that are used in industry.

Properties Are characteristics that describe a mineral such as color, luster, streak, etc. Color – The appearance of a mineral based upon the contained impurities. Luster - The manner in which a mineral’s surface reflects light. Streak – The color of the powdered mineral left behind when rubbed against an unglazed porcelain tile. Cleavage – The tendency of a mineral to break along smooth, flat surfaces. Fracture – The tendency of a mineral to break unevenly along curved or irregular surfaces.

Properties (cont.) Hardness – A mineral’s resistance to being scratched. Density – The measure of the amount of matter in a given space; the ratio of the mass to the volume. D=M/V. Special Properties: Characteristics that are particular to only a few types of minerals. Fluorescence – Certain minerals will glow when viewed with an ultraviolet light. Magnetism – Some minerals are natural magnets. Ex. : Magnetite a.k.a. loadstone. Radioactivity – Some minerals can contain elements that give off radiation. Ex. : Radium, Uranium.

The Formation of Minerals Evaporating Salt WaterEvaporating Salt Water – as water evaporates, minerals such as halite and gypsum are left behind. Surface & GroundwaterSurface & Groundwater – can carry dissolved minerals into bodies of water where they crystallize to form new minerals. Heat & PressureHeat & Pressure – can change the chemistry of the existing rocks to form metamorphic rocks. Hot Water SolutionsHot Water Solutions – occur when ground water sinks deeper to be heated by magma and react with minerals. PegmatitesPegmatites – teardrop shaped bodies with large crystals that form as magma moves upwards. PlutonsPlutons – magma that moves upwards then cools to form crystals.

Mining – The removal of rocks and minerals from the Earth. Ore 1.) Ore – A naturally occurring mineral that is mined for profit. Surface Mining 2.) Surface Mining – Removing deposits that are close to the surface in open pits or quarries. Subsurface Mining 3.) Subsurface Mining – Removing minerals that are located very deep within the Earth. Reclamation a.) Reclamation – The process in which the surface land is returned to it’s original, pre- existing state after mining has been completed. Recycling 4.) Recycling – The reuse of mined products to reduce our mineral needs.

Classes of Minerals Metallic MineralsMetallic Minerals – Minerals that have shiny surfaces and are good conductors of heat and electricity. Nonmetallic Minerals Nonmetallic Minerals – Minerals that are nonmetals, dull and are electrical insulators. GemstonesGemstones – A type on nonmetallic mineral that is highly valued for it’s beauty and rarity. The color of a gemstone is it’s most important and attractive characteristic. CaretCaret – A unit of mass for a gemstone. 1 caret= 200mg.