Atoms
Atoms – basic building blocks for all earth materials; consist of 3 basic components: protons, neutrons, electronsAtoms combine to form Elements
Elements – fundamental component that can not be broken down into other substances by ordinary chemical processesElements combine to form mineralsGeneral Facts About Minerals
2,000 + minerals have been identifiedA few are “native elements” -- made of only one element, such as sulfur, gold. copper, and graphite (carbon)Most are compounds, especially the silicate group (Si, O).Other important groups are oxides, carbonates, and sulfides.Gold (Au) Silver (Ag) Platinum (Pt) Diamond (C) Graphite (C) Sulfur (S) Copper (Cu)
MINERALSNATIVE ELEMENTS
Copper
Silver
Gold
Mineral Criteria
1. Crystalline solid – atoms have specific arrangement or crystal structure 2. Naturally occurring – not manufactured3. Have a definite chemical composition – may be a single element or combination4. Inorganic – minerals not made by living things (organic)MINERAL FORMATION
CRYSTALLIZE FROM MAGMA or LAVA solidification of liquid magma/lava to solid with a definite internal arrangement of atoms into a regular repeating pattern PRECIPITATE FROM SOLUTION dissolved minerals come out of solution (water) to form solidsMinerals are identified by their Physical Properties
Crystal Form – determines physical propertiesColorStreakLuster – metallic, non-metallic Hardness – Mohs Hardness Scale (1-10)CleavageFractureAcid Test for carbonate mineralsA mineral’s physical properties are controlled by its internal arrangement of atoms regularly repeating, orderly pattern
The most common crystalline structure
Silica-oxygen tetrahedron – basic building block for silicate mineralsSilica tetrahedron combine several different ways
Five major types of silicate minerals based on their structure Isolated tetrahedron Single chain C) Double chains D) Sheet silicates E) 3-D framework silicatesMinerals can have the same chemical composition (Carbon) but different physical properties because of their crystal structure
Diamond Graphite
COLOR
Color is not usually a definitive property of a mineral. Some minerals have characteristics colors Others vary due to chemical differences or impurities (atoms mixed inside the main elements) However most minerals have a variety of colors.
Some Colors of Quartz
STREAKFor opaque minerals, if you rub the sample across a streak plate, it will leave a colored powder. This streak is distinctive for minerals and is used to identify minerals.
Varieties of Hematite – all same color streak
HARDNESS – Mineral’s resistance to scratching or abrasion. Minerals with higher numbers will scratch minerals belowLUSTER – Does this look like it could be made from a hard metal? Describes how light reflects off the surface Categories: Metallic or Non-metallic Metallic – luster of metal – shines like a hard metal (light does not penetrate)Many non-metallic minerals are SHINY because they are transparent or semi-transparentNon-metallic: vitreous or glassy; silky; pearly; greasy; waxy, dull; earthy
Examples of metallic luster
Pyrite (FeS2) Galena (PbS)More Examples of Metallic Luster
PYRITE
GALENA
Example of non-metallic luster
Vitreous--quartzExample of non-metallic luster
Silky--example plagioclase feldsparNon-metallic and metallic luster – earthy hematite – metallic hematite
Cleavage and FractureSome minerals split along flat surfaces (called cleavage planes) when struck hard--this is called mineral cleavage Other minerals break unevenly along rough or curved surfaces--this is called fracture A few minerals have both cleavage and fracture ( mica )
FLUORITE
HALITEHalite (NaCl) Fluorite (CaF2)
Cleavage – due to weak bonds in the crystal structure
Cleavage
BIOTITEMUSCOVITE
Rose Quartz – Conchoidal Fracture
Conchoidal Fracture - QuartzObsidian
NONSILICATE MINERALS CARBONATES
Carbonate ion (CO32-) is prominent in minerals. Bonds generally weak. Minerals are soft (3-4). Minerals are soluble in acidic water. Leads to cave development. Calcite (CaCO3) if transparent can Break light into 2 images (double refraction)CALCITE