Presentation on theme: "Characteristics and Properties"— Presentation transcript:
1 Characteristics and Properties MINERALSCharacteristics and Properties
2 Mineral Characteristics What is a mineral?Naturally occuringNot man-made (synthetic) or biologically produced.Pearls, styrofoam, charcoal are not mineralsInorganicNot formed from processes involving organisms (living or once living)SolidHas definite chemical compositionAn element or compoundHas an orderly arrangement of atomsCrystalline structure-that is-atoms have repetitive patterns and internal structures are distinct.Geometric solids with smooth surfaces (crystal faces)Identifying Characteristics of MineralsColorColor by itself IS NOT sufficient to identify a mineralLusterHow the material reflects lightMetallic-shiny. Ex: silver, copper, etcNonmetallic-Pearly or cloudy, dullHardnessHow easily the mineral can be scratchedCan be compared to the hardness of other minerals by using the Mohs scaleStreakThe powder form of the mineral left on a porcelain plate (must be softer than the porcelain)CleavageThe way the mineral splits along flat surfacesDetermined by the arrangement of the atomsNot all minerals have cleavageDensityRatio of mass to volumeDetermined by the mass of the atoms and how close they are
3 Formation of Minerals How are minerals formed? One way is the cooling of magmaThermal energy is lost; atoms migrate together and form different compoundsThe elements present and the amounts determine the kind of mineralsDifferent crystal structures are formedIf the magma cools slowly, large crystals are formed. Different minerals form at different temperatures. Heavier minerals such as magnetite sink and lighter ones float.Minerals such as quartz and calcite form late in the cooling process and are known as hydrothermal minerals. In the last few years, hydrothermal vents have been formed on the ocean floor. In these areas, sea water filters into the hot crust and is heated to 400 degrees C. The hot water then reacts with the crust and becomes a metal bearing liquid. When it returns to the cooler sea floor, it deposits minerals, including iron, copper and zinc sulfide.--Minerals can precipitate out of a solutionWhen water is saturated with dissolved solids and can’t hold any more, the excess falls out of the solution. An example of this is the manganese nodules on the ocean floor--Minerals can form by evaporationMinerals such as salt, gypsum and calcite (calcite forms in two ways) are formed from sea water when it evaporates. This happens in warmer parts of the world where the sun's heat evaporates the water and leaves the minerals.Other ways that minerals are formed:Some minerals are formed from the weathering of rocks.Chemical changes are caused by atmospheric oxygen, water and acid rain. Such action can change feldspars to kaolin and pyrite (fools gold) into a brown iron ore called limoniteAnd lastly some minerals are formed when rocks are metamorphosed, that is subjected to heat and pressure.Minerals formed in this way include garnet and mica.
4 Mineral GroupsMinerals that contain oxygen and silicon are called “silicates”. These two minerals combine to form most of the minerals in the earth’s crust.They are the most abundant single minerals in the earth’s crust (oxygen-46.6%; silicon-27.7%)More than half of the minerals in the earth’s crust are feldspars which is a silicateSome other examples of silicates include: talc, quartz, mica, topaz, hornblende, garnet, zircon
5 Uses of Minerals Gems Ores Mining Rarity and beauty makes them valuableGemstones used for jewelry are cut and polished and sometimes don’t resemble the raw form of the mineralMay have a crystal structure that allows it to be cut in facetsMay have the addition of another mineral that gives it a brighter colorOresA mineral is an ore if it contains a substance that can be sold for profitHematite is the ore of ironBauxite is the ore of aluminumCopper comes from chalcopyrite oreRutile is the ore that titanium comes fromTitanium is valuable because of its strength and low density (lightness)Ore deposits are formed when fluids travel through weaknesses in rocks, such as fractures and cracks.The minerals dissolved in the fluids are left behind when the liquid evaporates, forming “vein depositsMiningOres are only profitable if the cost of mining them is less than the value of the material being minedWaste rock has to be removedThis can be expensive and harmful to the environment
6 Physical AppearanceColor cannot be used exclusively to identify minerals. For example the color of turquoise can vary from blue to greenMinerals may have varying degrees of transparency, which is the ability of light to pass through a substance—quartz can be transparent, but can contain flaws that make it translucent. This is related to Luster.Luster is definitely an identifying physical characteristicIt describes how light reflects from the surface of the mineral. Describers might include:Metallic, waxy, pearly, earthy, dull,glassy (vitreous), silky
7 HardnessThis is how easily a mineral can be scratched and is definitely an identifying characteristics. In order to be scratched by an object, the mineral must be softer than the object doing the scratching.The Mohs scale is a system of comparing the hardness of a list of 10 minerals (The Giant Cat Found a Foolish Quail that Couldn’t Dance)Developed by Frederich MohsIt lists them in order from 1 (softest) to 10It gives a list of common objects and their hardnessIf the mineral scratches the common object but the object won’t scratch the mineral, the mineral is the hardestMoh's Scale
8 Streak Streak is the color of the powder form of the mineral A streak plate is used to do this test. It is a piece of unglazed porcelain—which has a hardness of 7 on the Moh’s scale. A streak of the mineral is left on the porcelain when it is rubbed across with the mineral. The mineral must be softer than the streak plate if this is to work.Some minerals leave a certain color streak, which is an identifying characteristic.An example of this is hematite, which although it is a black mineral, leaves a red streak
9 Cleavage and FractureWhen a mineral breaks it does so either by fracturing or by cleaving. Crystal cleavage is a smooth break producing what appears to be a flat crystal face. Here are a few rules about cleavage. First cleavage is reproducible, meaning that a crystal can be broken along the same parallel plane over and over again. All cleavage must parallel a possible crystal face.Fracture describes the way a mineral breaks and is different from cleavage. A fracture might be splintery, conchoidal (like glass) , jagged or earthy (like a ball of clay)
10 Common MineralsThere are more than 4000 named minerals, but most rocks are made up of just a small number—these are the “rock forming” mineralsCentral Florida is the heart of the US phosphate industry and the leading producer of phosphate in the world. Phosphate is used to make fertilizerPhosphate is a profitable industry in FloridaMining for phosphate also produces toxic substances such as uranium and arsenic because the phosphate is buried under these substances. The by-products can’t be returned to the mine because they are a source of pollution
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