Identification of MineralsUsing Physical properties

Baker 7th grade scienceColor & StreakColor is the first thing someone notices when they view a mineral. color is not a good property to be used in the identification of minerals. Many minerals have different colors and some minerals' colors are identical to other minerals' colors.Streak is actually the color of the powder of a mineral.Pyrite (known as "Fool's Gold") is always brassy yellow when found in crystals, even broken crystals, of any size; but when powdered, produces a black streak. Gold's streak, by the way, is yellow!

Luster The way a mineral reflects a light luster.Either metallic or nonmetallic

Some other ways to describe luster are

Dull - just a non-reflective surface of any kind Earthy - the look of dirt or dried mud Fibrous - the look of fibers Greasy - the look of grease Gumdrop - the look a sucked on hard candy Metallic - the look of metals Pearly - the look of a pearl Pitchy - the look of tar Resinous - the look of resins such as dried glue or chewing gum Silky - the look of silk, similar to fibrous but more compact Submetallic - a poor metallic luster, opaque but reflecting little light Vitreous - the most common luster, it simply means the look of glass Waxy - the look of wax

Baker 7th grade scienceHow a mineral breaksWhen a mineral breaks it does so either by fracturing or by cleaving.Cleavage is the tendency of a mineral to break along flat surfaces. Crystal cleavage is a smooth break producing what appears to be a flat crystal face. Fracture is the tendency of a mineral to break into irregular pieces.

Cleavage (1 direction):Example: mica

Cleavage (2 directions):orthoclaseamphibole

Cleavage (3 directions):halitecalcite

FractureFracture refers to the non-planar breakage of minerals. Minerals that break along fractures (as oppose to cleavage planes) do not exhibit predictable weakness along specified bonds. Fractures may be described as splintery, uneven, or conchoidal.

Specific GravitySpecific gravity refers to the weight or heaviness of a mineral, and it is expressed as the ratio of the minerals weight to an equal volume of water.Water has a specific gravity of 1. Therefore, a mineral with a specific gravity of 1.5, is one and a half times heavier than water. Minerals with a specific gravity < 2 are considered light, 2-4 are average, and >4.5 are heavySpecific gravity can be measured using complex lab tools such as the hydrostatic balance or more simple procedures involving beakers and water displacement measurements.

Density:mass of a mineral divided by volume of the mineralmetallic minerals tend to have higher densities than non-metallic mineralsGalenaD=7.5 QuartzD=2.65

reaction with hydrochloric acid (calcite fizzes)Distinctive properties:taste (halite tastes salty)feel (talc feels soapy, graphite feels greasy)magnetism (magnetite attracts a magnet)double refraction (calcite when placed over printed material, letters appear doubled) smell (sulfur smells like rotten eggs)

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