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www.middleschoolscience.com 2009http://www.gc.maricopa.edu/earthsci/imagearchive/index.htmMinerals and RocksWhat is a mineral?SolidCannot be a liquid or a gasNaturally OccurringFound in nature, not man-madeInorganicIs not alive and never was, non-livingFixed compositionHas a chemical formula, most are formed from compounds of two or more elements, some minerals consist of one element ex. AuCrystal FormA definite structure in which atoms are arrangedQuestions to ask yourself when determining if an item is a mineral or not:Is it non-living material?Is it a solid?Is it formed in nature?Does it have a crystalline structure?The next few slide shows an assortment of items.

As a group, categorize the items as either:Minerals or Non-Minerals.

Gold

FossilTopaz

Bones

Granite

Quartz

Pearls

TalcIcebergs

Diamond

Coal

Rock SaltAnd the answers areMinerals

GoldTopazQuartzTalcIceberg*Diamonds

Non-Minerals

Wood - once livingFossils once livingBone - living materialGranite - intrusive igneous rock Pearls made by oystersCoal - Sedimentary rockRock Salt Sedimentary rockAccording to IMA ice is listed as a mineralWhat is a mineral?A mineral is a naturally formed, inorganic solid that has a definite crystalline structure.Mineral Identification BasicsPHYSICAL PROPERTIES HARDNESS HARDNESS is defined as the resistance a mineral has to being scratched - its scratchability. Hardness tests are done by scratching one mineral against another. The mineral that is scratched is softer than the other.

Pyrite Crystals Hardness of 6.5Mineral Identification BasicsPHYSICAL PROPERTIES HARDNESS MOHS SCALE OF MINERAL HARDNESS1. TALC2. GYPSUM3. CALCITE4. FLUORITE5. APATITE6. FELDSPAR7. QUARTZ8. TOPAZ9. CORUNDUM10. DIAMONDOTHER MATERIALS COMMONLY USED:2.5 - FINGERNAIL 3 - COPPER PENNY 5.5 - GLASS 6-6.5 - STEEL FILEMineral Identification BasicsPHYSICAL PROPERTIES CLEAVAGE CLEAVAGE is the property of a mineral that allows it to break repeatedly along smooth, flat surfaces.

These GALENA cleavage fragments were produced when the crystal was hit with a hammer. Note the consistency of the 90o angles along the edges.

These are FLUORITE cleavage fragments.Mineral Identification BasicsPHYSICAL PROPERTIES CLEAVAGE Within this crystalline pattern it is easy to see how atoms will separate to produce cleavage with cubic (90o) angles.Mineral Identification BasicsPHYSICAL PROPERTIES CLEAVAGE These pictures show different cleavage angles and the quality of cleavage.

Fluorite has cleavage in four directions

A thin sheet of Muscovite seen on edge.Mica has perfect cleavage in ONE direction.

Mineral Identification BasicsPHYSICAL PROPERTIES CLEAVAGE Common salt (the mineral HALITE) has very good cleavage in 3 directions.

These 3 directions of cleavage are mutually perpendicular resulting in cubic cleavage.

Mineral Identification BasicsPHYSICAL PROPERTIES STREAK STREAK is defined as the color of the mineral in powder form.Hematite on Streak Plate

Streak is normally obtained by rubbing a mineral across a streak plate. This is a piece of unglazed porcelain. The streak plate has a hardness of around 7 and rough texture that allows the minerals to be abraded to a powder. This powder is the streak.

Hematite has a reddish brown streak.Mineral Identification BasicsPHYSICAL PROPERTIES LUSTER LUSTER is defined as the quality of reflected light. Minerals have been grossly separated into either METALLIC or NON-METALLIC lusters. Following are some examples:

Native Silver has a Metallic LusterMineral Identification BasicsPHYSICAL PROPERTIES LUSTER METALLIC Stibnite

Galena

Marcasite

Pyrite Mineral Identification BasicsNON-METALLIC LUSTER VITREOUS Olivine - Peridot

Wulfenite

Spinel

QuartzMineral Identification BasicsNON METALLIC LUSTER Miscellaneous Lusters

Asbestos - Silky

Apophyllite - PearlyLimonite - Dull or Earthy

Sphalerite - Resinous

Graphite has a greasy or submetallic luster and easily marks paper.Mineral Identification BasicsPHYSICAL PROPERTIES COLOR The COLOR of a mineral is usually the first thing that a person notices when observing a mineral. However, it is normally NOT the best physical property to begin the mineral identification process.Following are some examples of color variation within mineral species followed by minerals that have a distinctive color:Various colors of CALCITE.

Clear - Without ImpuritiesMineral Identification BasicsPHYSICAL PROPERTIES COLOR Various colors of Quartz.

Hematite Inclusions

Chlorite inclusions

AmethystIonic IronMineral Identification BasicsINDICATIVE COLOR Turquoise

Sulfur

Malachite

Rhodochrosite

AzuriteMineral Identification BasicsPHYSICAL PROPERTIES SPECIFIC GRAVITY The SPECIFIC GRAVITY of a mineral is a measure of the minerals density. It is related to the types of elements that make up the mineral and how they are packed into the minerals atomic structure.

Gold in QuartzGold has a Specific Gravity of 19.2. It is 19.2 times the weight of an equal volume of water. Water has a Specific Gravity of 1.Mineral Identification BasicsPHYSICAL PROPERTIES SPECIFIC GRAVITY The SPECIFIC GRAVITY of a mineral is determined by weighing the specimen in air and then weighing it in water. It is the ratio of an objects density to the density of water.

(Weight in air) - (Weight in water )Weight in airSpecific Gravity = Mineral Identification BasicsPHYSICAL PROPERTIES TASTE IT IS NOT RECOMMENDED THAT A TASTE TEST BE PERFORMED ON MINERALS AS A STANDARD PROCESS. SOME MINERALS ARE TOXIC. However, the mineral HALITE is common salt and has a unique taste.

Halite cubes from Trona, CAMineral Identification BasicsPHYSICAL PROPERTIES MAGNETISM MAGNETISM is the ability of a mineral to be attracted by a magnet. This most commonly is associated with minerals rich in iron, usually magnetite.

This is a piece of MAGNETITE with a magnet adhering to it. Magnetite is strongly magnetic in that a magnet will easily be attracted to it.Mineral Identification BasicsPHYSICAL PROPERTIES DIAPHANEITY The manner in which minerals transmit light is called DIAPHANEITY and is expressed by these terms:

TRANSPARENT: A mineral is considered to be transparent if the outline of an object viewed through it is distinct. TRANSLUCENT: A mineral is considered to be translucent if it transmits light but no objects can be seen through it. OPAQUE: A mineral is considered to be opaque if, even on its thinnest edges, no light is transmitted. Quartz with Spessartine GarnetsMineral Identification BasicsPHYSICAL PROPERTIES DIAPHANEITY TRANSPARENT: A mineral is considered to be transparent if the outline of an object viewed through it is distinct.

Topaz from Topaz Mountain, UtahMineral Identification BasicsPHYSICAL PROPERTIES DIAPHANEITY Sylvite from Salton Sea, California

TRANSLUCENT: A mineral is considered to be translucent if it transmits light but no objects can be seen through it.

Backlit Apophyllite CrystalsMineral Identification BasicsPHYSICAL PROPERTIES DIAPHANEITY Schorl - The black variety of TourmalineOPAQUE: A mineral is considered to be opaque if, even on its thinnest edges, no light is transmitted.

Investigation Question: Which physical characteristics are useful when identifying minerals? Mineral #Mineral #Record DataRecord Data