Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Minerals
Document related concepts
Transcript
MINERALS Learning Target = Matter & Minerals Mineral Characteristics Definition = naturally occurring, inorganic solid with an orderly crystalline structure and a definite chemical composition To be considered a mineral, must have the following characteristics: Naturally occurring Solid substance Orderly crystalline structure Definite chemical composition Generally considered inorganic Mineral Characteristics Naturally occurring – formed by geologic processes Solid substance – solids within temp ranges that are normal for Earth’s surface Crystalline structure – atoms or ions arranged in orderly & repetitive manner Definite chemical composition – most minerals are chemical compounds Generally considered inorganic – minerals generally do not come from a living source How Minerals Form 4 major processes by which minerals form: Crystallization from Magma Precipitation Pressure & Temperature Hydrothermal Solutions How Minerals Form Crystallization from Magma As magma (molten rock) cools, elements combine and crystallize 1st – compounds rich in Fe, Ca, Mg 2nd – Na, K, Al Muscovite Feldspar Horneblende Quartz How Minerals Form Precipitation Water contains dissolved substances Minerals form due to: Evaporation Temperature Minerals change are left behind How Minerals Form Pressure & Temperature Increase in pressure causes a mineral to recrystallize Form more compact minerals Temperature change can cause instability and new minerals form that are stable at new temperature Ex: Talc & Muscovite How Minerals Form Hydrothermal Hot Solutions mixture of water & dissolved substances Temps = 100°C & 300°C Chemical reactions form new minerals Solutions cool & minerals form as well Ex: Quartz, pyrite, sulfur minerals Mineral Groups Over 3,800 identified minerals Groups are based on composition Silicates Carbonates Oxides Sulfates & sulfides Halides Native elements Silicates Silicon & oxygen = most abundant elements in Earth’s crust Si and O combine & form the silicon-oxygen tetrahedron (SiO4) Usually contain other elements Si-O tetrahedra join in different ways & bonds are strong Olivine Augite Hornblende Mica Quartz Silicates Crystallization from magma Cooling occurs at or near Earth’s surface (temp and pressure low) Also form at great depths (T & P ↑) Silicate formation dependent on: Place of formation Chemical composition of magma Carbonates 2nd most common group Contain C, O & another metallic element Calcite (CaCO3) is most common Ex: Dolomite, limestone (rock), marble (rock) Oxides Contain O + 1 or more elements (usually metals) Form by: Magma cooling Changes in T and P Exposed to water or moisture in air Ex: Rutile (TiO2), Corndum (Al2O3), Hematite (Fe2O3) Sulfates & Sulfides Contain Sulfur Form when mineralrich waters evaporate Form from thermal solutions Ex: Gypsum, Galena, Pyrite Halides Contain a halogen ion plus 1 or more elements Ex: Halite (NaCl) & Fluorite (CaF2) Native Elements Contains one element Ex: Gold (Au), Silver (Ag), Copper (Cu), Sulfur (S), Carbon (C) Native forms of carbon are graphite & diamond Some form from hydrothermal solutions Properties of Minerals Color Streak Luster Crystal form Hardness Cleavage Fracture Density Distinctive properties Properties of Minerals Color Can be unique to some minerals Not useful in identification Small amounts of different elements can give the same mineral different colors Ex: Sapphires Properties of Minerals Streak Color of a mineral in its powdered form Rub mineral across a streak plate Mineral color may vary but streak does not Difference between minerals with metallic & nonmetallic lusters Properties of Minerals Luster How light is reflected from the surface of a mineral Metallic luster – appearance of metal Nonmetallic luster – use different adjectives Glassy Pearly Silky Earthy Brilliant or vitreous Properties of Minerals Crystal form Visible expression of a mineral’s internal arrangement of atoms When a mineral forms slowly with plenty of space, develop into a crystal with well-formed sides Most of the time, minerals compete for space so minerals do not show their crystal form Properties of Minerals Hardness Measure of the resistance of a mineral to being scratched Determined by rubbing one mineral against another of known hardness Mohs scale consists of 10 minerals arranged from 10 (hardest) to 1 (softest) Properties of Minerals Cleavage Tendency of a mineral to break along flat, even surfaces Properties of Minerals Fracture Uneven breakage of a mineral Minerals that do not show cleavage when broken are said to fracture Properties of Minerals Density Property of all matter that is the ratio of an object’s mass to its volume Unit = grams per cubic centimeter (g/cm3) Many common minerals have densities between 2 & 5 g/cm3 Properties of Minerals Distinctive Properties of Minerals Some minerals can be recognized by other distinctive properties Feel (Talc = soapy, graphite = greasy) Easily shaped (Gold, silver, copper) Magnetic Double refraction (appearance doubles) Smell (sulfur minerals = rotten eggs) Reacts with hydrochloric acid
