Mineral Properties & Identification

The story of minerals so far…. Minerals formed from elements that originated in exploding stars, made a nebula and then formed our solar system Minerals are solid, naturally occurring, inorganic, made of chemical elements and have an internal arrangement of atoms (crystal structure) Native minerals are made of 1 element: gold, sulfur, iron Top elements that make up the Earth’s crust are: oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium Most minerals are compounds: NaCl, CaCO 3 SiO 2 A rock is a mixture of 1 or more minerals: granite Limestone is made of only one mineral – calcite.

Observe Minerals #1 - #39 Separate/Group the minerals by properties: – How are they alike? – How are they different? – Regroup them again using another similar property.

Properties used to Identify Minerals Color Odor Shiny or dull (Luster) Hardness (scratches) Streak color (on streak plate) Solubility in water Dissolve in water or react in acid Cleavage (split or shatter when hammered)

More properties to I.D. minerals Optical properties: double refraction Magnetic Heavy (specific gravity) Crystal shape Fluorescent Taste? Radioactive

1 Hand lens1 yellow 1 Penny2 clear 1 Glass plate2 pink 2 Streak plates1 dark red 1 magnet1 flat 1 Nail1 gold 8 minerals

Mineral I.D. Lab

Physical Properties of Minerals Color: light or dark, yellow, gold, pink…. Luster: –metallic, –Non-metallic: dull, glassy, vitreous, pearly, adamantine Light Interaction: –Opaque: not allowing light to pass through –Translucent: “cloudy”; some light passes through but not able to see clear detail –Transparent: allows light to pass through and detail can be seen clearly

Streak The color of the mineral in its powdered form. Rubbing the mineral on a streak plate. Streak is more reliable than color: Streak is a consistent property of a mineral. Metallic minerals generally have a dark streak, –Non-metallic mineral do not Two different colored forms of the SAME mineral: SAME colored streak

Mohs scale of hardness Hardness Relative scale: comparing the hardness of a mineral to a known object Diamond being the hardest 10 Talc is the softest 1

Fracture Quartz (glass) fractures and shatters into irregular-shaped pieces with no flat planes Cleavage: the tendency of a mineral to break along flat planes of weak bonding Halite will cleave into many smaller pieces each with 3 planes at 90°

Three examples of perfect cleavage – 3 flat planes (sides) fluorite, halite, and calcite

Mineral Specimen Number Color Luster Light interaction Streak color Hardness number Cleavage Or Fracture Soluble in water Solubility in acid Other Properties: Magnetism, Fluorescence Mineral name page yellow dull opaque yellow 1-2fracture insoluble insoluble Smells like rotten eggs sulfur

NameColor Luster Light Interaction StreakHard- ness CleavageSmellSol. water Sol. acid 1 Yellow Dull OpaqueYellow1-2noneRotten Egg! IS 2Gold, metallic, shiny opaqueblack6none ISSS? 3 white Pearly, flat Transparent translucent none2-3Perfect! 1 direction peels noneIS 4 Clear shiny Transparent Double refraction None white 3perfectnoneISYES! FIZZ 5 Clear, white Shiny, Tastes salty translucentnone2-2.5Perfect! 3 direction 90° angle noneYes! dis- solve s IS 6 Dark red- brown dull opaqueRed- brown 3-4noneNone or earthy ISSS 7 Salmon pinkopaquenone6Good 2 direction noneIS 8 Pink, clear glassy translucentnone7None fractures concoidal noneIS sulfur Pyrite Mica (Muscovite) calcite Halite (Salt) hematite feldspar Quartz

Determining the Specific Gravity of a Mineral 1.Get out a piece of notebook paper. 2.Title: SpG & Mineral I.D. (pg ) 3.Copy Data Table 1 on page Copy the formula on pg Collect the data using a balance 7.Use the table on pg. 113 to Identify the mineral 8. Answer questions #3-8 on page 113

Determining Specific Gravity Mineral DataMass (g) Mass in air Mass suspended in water Change in mass from air to water Specific Gravity (calculated) Specific Gravity (accepted value) Name of mineral SpG = Mass of mineral in air change in mass

Suspend the mineral from a piece of string in a beaker of water. Find its mass.

So, according to your data, which has a higher specific gravity? Metals or non-metals?

Specific Gravity of Some Common Minerals SpG Sulfur2.1 Gypsum2.3 Calcite2.7 Chalcopyrite4.2 Pyrite5.0 Magnetite5.2 Galena7.2

Practice Calculate the Specific Gravity of the mineral using the mass measurements. Mass in air: 15.0 g Mass in water-12.0 g SpG = What mineral is this? 3 g Mass in air Loss of mass 15.0 g 3.0 g = 5.0

Mineral Flow Chart in your notebooks copy the chart below Color? dark or light_______________ Luster? Metallic or non-metallic ________ Streak? Black, brown or reddish________ Harder than glass? __________________ Cleavage? Yes, no cleavage, 1,2,3,4 planes Mineral Name _____________