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Mineral Groups. All others: 1.5% Element Abundances Silica (SiO 4 ) 4- SILICATES Common cations that bond with silica anions Mineral Groups.

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Presentation on theme: "Mineral Groups. All others: 1.5% Element Abundances Silica (SiO 4 ) 4- SILICATES Common cations that bond with silica anions Mineral Groups."— Presentation transcript:

1 Mineral Groups

2 All others: 1.5% Element Abundances Silica (SiO 4 ) 4- SILICATES Common cations that bond with silica anions Mineral Groups

3 Ferromagnesian Silicates (Fe, Mg) Non-ferromagnesian Silicates (K, Na, Ca, Al) Oxides Carbonates Sulfides/sulfates Native elements Mineral Groups

4 Actinolite (Tremolite) Ca 2 (Mg,Fe) 5 Si 8 O 22 (OH) 2 Subclass: Amphibole Streak: White Hardness: 5 – 6 Lustre: Vitreous Density: Habit: Aggregate of acicular grains Colours: Greenish - white Crystal System: Monoclinic Cleavage: Uneven Fracture: Subconchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Habit and colour are best indicators. Associations: Metamorphosed calcareous sediments Comments: Higher in Fe than tremolite. Silicates

5 Antigorite (Serpentine) Mg 3 Si 2 O 5 (OH) 4 Subclass: Phyllosilicate Hardness: Streak: White Density: 2.6 Lustre: Greasy or waxy Habit: Lath-shaped crystals. Colours: Shades of green Crystal System: Monoclinic Cleavage: Perfect basal Fracture: Splintery or conchoidal Magnetism: None Reaction with HCl: Unknown Identification in hand sample: Lustre, colour and habit are indicative. Associations: Formed by hydrothermal action of mafics and ultramafics. Associations may include talc, calcite, brucite, chlorite, magnetite and chromite. Silicates

6 Augite (Ca,Na)(Mg,Fe,Al,Ti)(SiAl) 2 O 6 Subclass: Pyroxene Hardness: 5.5 – 6 Streak: White or gray Density: Lustre: Vitreous Habit: Small blocky grains. Colours: Dark-greeny black colour Crystal System: Monoclinic Cleavage: Good / Uneven Fracture: Uneven to conchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Colour, cleavage and hardness are indicative of a pyroxene. Augite has 2 cleavage planes at 90°. Associations: Found in mafic to ultramafic rocks, and in high-grade metamorphs. Industrial / ecomonic uses: None. Silicates

7 Biotite K(Mg,Fe) 3 (AlSi 3 O 10 )(OH) 2 Subclass: Phyllosilicate Hardness: 2 – 3 Streak: Colourless Density: Lustre: Vitreous Habit: Micaceous Colours: Brown, black, reddish brown Crystal System: Monoclinic Cleavage: Perfect basal Fracture: Uneven Magnetism: None Reaction with HCl: Very weak Identification in hand sample: Colour and habit Associations: A very common mineral found in igneous, metamorphic and sedimentary rocks. Industrial / ecomonic uses: Altered into vermiculite, biotite is used as an insulation material and as filler in certain building supplies. Silicates

8 Chalcedony (Micro/Cryptocrystalline Quartz) -- SiO 2 Subclass: Framework Hardness: 7 Streak: White Density: 2.7 Lustre: Vitreous / almost waxy Habit: Aggregate of very tiny SiO 2 grains. Colours: White/gray or any colour Crystal System: Hexagonal Cleavage: None Fracture: Conchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Identified by hardness and texture/habit. Associations: Abundant in felsic rocks. Industrial / ecomonic uses: Used for making glass and as a source of Silicon. Silicates

9 Chlorite (Mg,Fe,Al) 3 (Si,Al) 4 O 10 (OH) 2 Subclass: Phyllosilicate Hardness: Streak: Greenish white to white Density: Lustre: Vitreous to somewhat pearly, waxy, dull Colours: Greenish-black (typical) Crystal System: Monoclinic Cleavage: Perfect {001} Magnetism: None Reaction with HCl: None Identification in hand sample: Colour and its low hardness are distinguishing characteristics. Industrial / ecomonic uses: None, however chlorite schist sometimes does have ornamental uses. Silicates

10 Chrysotile (Serpentine) Mg 3 Si 2 O 5 (OH) 4 Subclass: Phyllosilicate Hardness: 2.5 Streak: White Density: 2.5 Lustre: Silky Habit: Fibrous Colours: Shades of green Crystal System: Monoclinic Cleavage: None Fracture: Uneven Magnetism: None Reaction with HCl: Unknown Identification in hand sample: Habit and colour and most indicative properties. Associations: Found by hydrothermal alteration of mafics and ultramafics. Associated with talc, calcite, brucite, chlorite, magnetite and chromite. Industrial / ecomonic uses: Used in 98% of world's production of asbestos. Silicates

11 Epidote Ca 2 (Fe,Al) 3 (SiO 4 ) 3 (OH) Subclass: Sorosilicate Hardness: 6 – 7 Streak: White Density: Lustre: Vitreous Habit: Aggregate of small grains, striated faces, small but visible crystals Colours: Greeny, yellow-green, black Crystal System: Monoclinic Cleavage: Perfect Fracture: Uneven Magnetism: None Reaction with HCl: None Identification in hand sample: Slight colour difference between this mineral and olivine, but only under magnification (where details in the crystals can be seen). Also indicitive is the presence of a cleavage plane. Associations: Common accessory mineral in many regional and contact metamorphed rocks, particularly in more iron-rich rocks. Industrial / ecomonic uses: Semiprecious gemstone Silicates

12 Garnet (Pyrope, Grossular, Almandine)(Mg,Fe,Ca) 3 Al 2 (SiO 4 ) 3 Hardness: 6.5 – 7 Streak: White Density: 3.8 Lustre: Vitreous Habit: Small, well-formed crystals Colours: Darker reddy colours Crystal System: Isometric Cleavage: None Fracture: Conchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Crystal habit, colour and hardness. Industrial / ecomonic uses: Abrasives (particularly sandpaper), semi-precious gemstone. Silicates

13 HornblendeCa 2 (Mg,Fe) 4 Al(Si 7 Al)O 22 (OH,F) 2 Subclass: Amphibole Hardness: 5 – 6 Streak: White or gray Density: Lustre: Vitreous Habit: Intergrown crystals, prismatic character of grains. Colours: Black Crystal System: Monoclinic Cleavage: 2 at 56° and 124° Fracture: Uneven / conchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Prominent striations, prismatic crystals and angle on cleavages is distinguishing. Associations: Forms in igneous rocks, and in the metamorphic rock amphibolite. Industrial / ecomonic uses: Ornamental. Silicates

14 Muscovite KAl 2 (AlSi 3 O 10 )(OH) 2 Subclass: Phyllosilicate Hardness: 2.5 – 4 Streak: Colourless Density: Lustre: Vitreous Habit: Micaceous Colours: Colourless, to white or gray Crystal System: Monoclinic Cleavage: Perfect basal Fracture: Uneven Magnetism: None Reaction with HCl: None Identification in hand sample: Colour and habit are best indicators. Industrial / ecomonic uses: Used in the electronics industry in the manufacture of capacitors, transistors, insulators and certain window types. Also used as a filler in building materials. Silicates

15 Olivine (Forsterite (Mg) and Fayalite (Fe))Mg 2 SiO 4 - Fe 2 SiO 4 Subclass: Nesosilicate Hardness: 6.5 – 7 Streak: Colourless Density: Lustre: Vitreous Habit: Granular Colours: Pistachio green, greenish yellow brown Crystal System: Orthorhombic Cleavage: Imperfect Fracture: Conchoidal Magnetism: None Reaction with HCl: Very weak Identification in hand sample: Pistachio-green colour and granular habit. Associations: Mafic and ultramafic igneous rocks. Associated with Ca-plag, Industrial / ecomonic uses: Peridote (a translucent variety of olivine) is considered a 'gem' mineral. Also used as a refractory sand and infrequently as an abrasive. Silicates

16 Orthoclase KAlSi 3 O 8 Hardness: Streak: White Density: 2.6 Lustre: Vitreous Habit: Polysynthetic twinning Colours: Pinky-white Crystal System: Orthorhombic Cleavage: Perfect Fracture: Subconchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Colour and evidence of exsolution with plagioclase. Associations: Very common in granite, granodiorite, syenite and related felsic rocks. Silicates

17 Quartz (crystal) SiO 2 Hardness: 7 Lustre: Vitreous / glassy Density: 2.7 Habit: Crystalline Colours: Clear transparent Crystal System: Hexagonal Cleavage: None Fracture: Conchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Hardness, translucency and colour are indicators. Silicates

18 Talc Mg 3 Si 4 O 10 (OH) 2 Subclass: Phyllosilicate Hardness: 1 Streak: White Density: Lustre: Greasy Habit: Compact masses, often no crystals. Colours: White, or brownish, dark green, gray Crystal System: Monoclinic Cleavage: Perfect Fracture: Uneven Magnetism: None Reaction with HCl: Unknown Identification in hand sample: Mineral is very soft and are often compact masses. Colour is typical and varies to brown, green or gray. Silicates

19 Topaz Al 2 SiO 4 (F,OH) 2 Hardness: 8 Streak: White Density: 3.5 Lustre: Glassy Habit: Prismatic crystals Colours: Almost brownish, any colour Crystal System: Orthorhombic Cleavage: Perfect Fracture: Subconchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Resembles quartz, but harder. Associations: Quartz Industrial / ecomonic uses: Gemstone Silicates

20 Zircon (ZrSiO 4 ) Hardness: 7.5 Streak: White Density: Lustre: Subadamantine Habit: Excellent tetragonal prisms Colours: Colorless, red, brown, yellow, green or gray Crystal System: Tetragonal Cleavage: Imperfect Fracture: Conchoidal Magnetism: None Reaction with HCl: Unknown Identification in hand sample: Excellent crystalline habit, density and streak/colour are indicative. Industrial / ecomonic uses: Source of zirconium and hafnium Silicates

21 Azurite ---Cu 3 (CO 3 ) 2 (OH) 2 Hardness: 3.5 – 4 Streak: Lighter blue Density: 3.8 Lustre: Vitreous, earthy (fine grained) Habit: Fine grained coating or fracture filling on rock Colours: Azure blue Crystal System: Monoclinic Cleavage: Perfect Fracture: Conchoidal Magnetism: None Reaction with HCl: Strong Identification in hand sample: Colour is reliable, association with malachite is also indicative. Associations: Common mineral in the near-surface oxidized portion of copper-bearing hydrothermal sulfide mineral deposits. Associated with malachite. Industrial / ecomonic uses: A minor ore of copper, also has ornamental uses. Sometimes a pigment (when powdered). Carbonates

22 Aragonite ----CaCO 3 Hardness: 3.5 – 4 Lustre: Vitreous Streak: White Habit: Stalactitic aggregate of crystals or grains. Colours: Colourless or white Crystal System: Orthorhombic Cleavage: Pinacoidal Fracture: Subconchoidal Magnetism: None Reaction with HCl: Strong Identification in hand sample: Stalactitic habit, hardness (greater than that of calcite) and colour. Associations: Occurs in carbonate-bearing blueschist metamorphic rocks. Associated with glaucophane, lawsonite, pumpellyite. Also forms at or near the surface in cave and hot spring deposits. Industrial / ecomonic uses: Same as calcite, however abundance is much much less than that of calcite, thus having little economic value. Carbonates

23 Calcite (massive) CaCO 3 Hardness: 3 Density: 2.7 Streak: White Lustre: Vitreous Habit: Fine grained aggregates (massive) Colours: Colourless, white, gray, yellow-brown, pink, rose red Crystal System: Hexagonal Cleavage: Perfect rhombohedral Fracture: Subconchoidal Magnetism: None Reaction with HCl: Strong Identification in hand sample: Recognized by hardness and cleavage. Dolomite and aragonite have higher densities. Associations: Common as a cementing agent in clastic sediments, or as fossil fragments. Essential constituent of limestone. Industrial / ecomonic uses: Used in the manufacture of portland cement (quicklime). Also used as a pharmaceutical (antacids, calcium supplements). Carbonates

24 Calcite (sparry) (Iceland Spar) ---- CaCO 3 Hardness: 3 Streak: White Density: 2.7 Lustre: Vitreous Habit: Large crystals, some exhibiting common twin striae Colours: White Crystal System: Hexagonal Cleavage: Perfect rhombohedral Fracture: Subconchoidal Magnetism: None Reaction with HCl: Strong Identification in hand sample: Hardness, crystal habit and twin striae are typical. Associations: Common as a cementing agent in clastic sediments or as fossil fragments. Industrial / ecomonic uses: Used in the manufacture of portland cement (quicklime) and in the pharmaceutical industry. Comments: The transparent variety is called "Iceland Spar". Carbonates

25 Dolomite ---- CaMg(CO 3 ) 2 Hardness: 3.5 – 4Streak: White Density: 2.85Lustre: Vitreous Habit: Crystalline or aggregate, some with twin striae. Colours: Pinky/peach, white, gray, brown. Crystal System: Hexagonal Cleavage: Perfect rhombohedral Fracture: Subconchoidal Magnetism: None Reaction with HCl: Weak Identification in hand sample: Harder than calcite Associations: Major constituent of dolostone (aka dolomite). Industrial / ecomonic uses: Used in manufacture of portland cement. Carbonates

26 Malachite ---- Cu 2 (CO) 3 (OH) 2 Hardness: 3.5 – 4 Streak: Pale green Density: 4.0 Lustre: Earthy Habit: Very fine grained coating on other rocks, almost looks like paint. Colours: Copper green Crystal System: Monoclinic Cleavage: Perfect Fracture: Subconchoidal Magnetism: None Reaction with HCl: Strong Identification in hand sample: Colour is primary indicator, as well as habit. Associations: Common in near-surface oxidized portions of copper bearing hydrothermal sulfide mineral deposits. Industrial / ecomonic uses: Used as a minor ore of copper and also has ornamental uses due to vivid green colour. Carbonates

27 Siderite ---- FeCO 3 Hardness: 3.5 – 4Streak: White Density: 4.0 Lustre: Vitreous Habit: Aggregate of crystals or grains Colours: Tan brown (typical) Crystal System: Hexagonal Cleavage: Perfect rhombohedral Fracture: Uneven Magnetism: None Reaction with HCl: Weak Identification in hand sample: Identified by colour and hardness. Associations: Produced by hydrothermal alteration of limestone. May also occur as concretionary or oolitic forms in clay ironstones. Industrial / ecomonic uses: Sometimes used as an iron ore. Also used in pigments where a red or brown colour is desirable. Carbonates

28 Fluorite --- CaF 2 Hardness: 4 Streak: White Density: Lustre: Vitreous Habit: Crystals, usually cubic Colours: Commonly colourless, blue, purple or green, but any is possible. Crystal System: Isometric Cleavage: Perfect octahedral Fracture: Conchoidal Magnetism: None Reaction with HCl: Unknown Identification in hand sample: Cubic crystals, hardness and colour indicative. Associations: Common in hydrothermal mineral deposits associated with sulfides, carbonates and barite. Industrial / ecomonic uses: Main source of fluorine (which is added to drinking water, toothpaste, used as a flux in industrial uses and as part of CFCs) Halides

29 Halite (Salt) --- NaCl Hardness: 2 Streak: White Density: Lustre: Waxy Habit: Crystalline (cubic) Colours: Colourless or white if pure, any colour if not Crystal System: Isometric Cleavage: Cubic Fracture: Conchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Has a salty taste. Cubic cleavage and hardness are indicative for the less brave geologists. Associations: Abundant in marine evaporite deposits and may form beds hundreds to over a thousand meters thick. Associated minerals include calcite, dolomite, gypsum, anhydrite and sylvite. Halides

30 Limonite-- FeO(OH) Hardness: Streak: Yellow-brown Density: Lustre: Earthy Habit: Fine grained aggregate, powdery coating. Colours: Orange, yellow-brown Crystal System: Unknown Cleavage: None Fracture: Uneven Magnetism: None Reaction with HCl: Very weak Identification in hand sample: Colour is best indicator, followed by habit. Associations: Common weathering product of iron-rich rocks. Comments: The fine brownish coloured mineral is usually weathered goethite. Hydroxide

31 Chromite (FeCr 2 O 4 ) Hardness: 5.5 Streak: Brown Density: Lustre: Metallic to pitchy Habit: Fine grained aggregate. Colours: Black Crystal System: Isometric Cleavage: None Fracture: Uneven Magnetism: Weak Reaction with HCl: Unknown Identification in hand sample: Resembles magnetite and ilmenite, but not very magnetic and has a more resinous lustre. Associations: Found in mafic and ultramafic igneous rocks such as gabbro, peridotite, dunite and pyroxenite as an accessory mineral. Industrial / ecomonic uses: Only ore mineral for chromium. Oxides

32 Corundum (Al 2 O 3 ) Hardness: 9 Streak: White Density: Lustre: Vitreous to adamantine Habit: Well-formed crystals Colours: Any. White, gray or gray-blue, or red (ruby), blue (sapphire), yellow, green. Crystal System: Hexagonal Cleavage: None Fracture: Conchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Hardness is best indicator, crystal habit is good too. Associations: Gem quality corundum comes from metamorphed limestone or dolostone (needs high Al concentrations, here presumably from detrital deposits) Industrial / ecomonic uses: Used as a gemstone. High-quality ruby can be more valuable than diamond. Corundum is also used as an abrasive in sandpaper, polishing compounds, etc. Oxides

33 Hematite (massive) -- (Fe 2 O 3 ) Hardness: 5 – 6 Streak: Deep red Density: 5.3 Lustre: Earthy Habit: Very fine grained aggregate of red crystals. Colours: Deep red Crystal System: Hexagonal Cleavage: None Fracture: Subconchoidal Magnetism: Weak Reaction with HCl: Unknown Identification in hand sample: Deep red streak and earthy lustre are indicative. SG may also be indicative. Associations: Produced by weathering or hydrothermal alteration of iron-bearing minerals. May be found in some syenite, trachyte, granite and rhyolite. Industrial / economic uses: Important ore or iron, sometimes used as a gemstone. Comments: May become magnetic when heated. Oxides

34 Hematite (specular) (Fe 2 O 3 ) Hardness: 5 – 6 Streak: Deep red Density: 5.3 Lustre: Metallic Habit: Micaceous/tabular habit. Colours: Steel gray Crystal System: Hexagonal Cleavage: None Fracture: Subconchoidal Magnetism: None Reaction with HCl: Unknown Identification in hand sample: Shining gray metallic lustre and deep-red streak are indicative. Associations: Produced by weathering and hydrothermal alteration of iron-bearing minerals. Industrial / ecomonic uses: Important ore of iron. Oxides

35 Magnetite (Fe 3 O 4 ) Hardness: Streak: Black Density: 5.2 Lustre: Dull metallic to splendent Habit: Granular habit of fine grains. Some octahedral crystals may form. Colours: Black Crystal System: Isometric Cleavage: None Fracture: Subconchoidal Magnetism: Strong Reaction with HCl: Unknown Identification in hand sample: Highly magnetic. Habit and colour are also indicators. Associations: Very common accessory mineral found in a wide variety of igneous and metamorphic rocks, usually as small grains. Industrial / ecomonic uses: Mined for iron. Crushed magnetite also been used as aggregate to make high-density concrete for specialized applications, such as nuclear reactors. Oxides

36 Pyrolusite (MnO 2 ) Hardness: Streak: Black Density: 5.1 Lustre: Earthy Habit: Massive, compact, columnar or fibrous. Prismatic crystals are rare. Sometimes forms as dendritic coatings on other rocks. Colours: Black Crystal System: Tetragonal Cleavage: Perfect Fracture: Uneven Magnetism: None Reaction with HCl: Very weak Identification in hand sample: Will leave sooty marks if touched. Associations: Found in bog and marine deposits Industrial / ecomonic uses: Manganese is used to colour bricks. Oxides

37 Apatite Ca 5 (PO 4 ) 3 ( OH,F,Cl) Hardness: 5 Streak: White Density: Lustre: Vitreous, glassy Habit: Massive Colours: Grayish blue-green, or any. Crystal System: Hexagonal Cleavage: Poor Fracture: Conchoidal Magnetism: None Reaction with HCl: Weak Identification in hand sample: Colour, crystal habit and hardness are good indicators. Associations: Common accessory mineral in all environments. Industrial / ecomonic uses: Source of phosphate used in fertilizers and other industrial applications. Fluorine is also extractable from apatite. Comments: Same stuff as in bones and teeth. Phosphates

38 Alabaster (Gypsum) CaSO H 2 O Hardness: 2 Streak: White Density: 2.3 Lustre: Vitreous Habit: Granular / massive form of gypsum Colours: Colourless or white (typical) Crystal System: Monoclinic Cleavage: Perfect Fracture: Splintery Magnetism: None Reaction with HCl: Weak Identification in hand sample: Identified by hardness and good cleavage. Associations: Common in marine evaporite deposits. Industrial / ecomonic uses: Modern use is in gypsum wallboard used in construction. Used as an ornamental stone and for sculpture due to its softness. Sulfates

39 Barite (BaSO 4 ) Hardness: Streak: White Density: 4.5 Lustre: Vitreous Habit: Fine grained aggregates Colours: Colourless, white, gray, yellowish, brown, reddish, bluish or greenish Crystal System: Orthorhombic Cleavage: Perfect Fracture: Uneven Magnetism: None Reaction with HCl: None Identification in hand sample: High specific gravity is best indicator, colour and fracture are also helpful. Associations: Common in hydrothermal veins, associated with galena, sphalerite, pyrite, quartz, fluorite and carbonates. Industrial / ecomonic uses: Primary ore for barium, also used as an additive to drilling mud (because of high SG). Has over 2000 uses in industry. Sulfates

40 Selenite (Gypsum) CaSO H 2 O Hardness: 2 Streak: White Density: 2.3 Lustre: Vitreous Habit: Large crystalline habit Colours: Colourless, clear Crystal System: Monoclinic Cleavage: Perfect Fracture: Splintery Magnetism: None Reaction with HCl: Weak Identification in hand sample: Single large crystals of gypsum, typified by hardness and transparency. Associations: Found in marine evaporites. Industrial / ecomonic uses: Used in gypsum wallboard. Sulfates

41 Chalcocite (Cu 2 S) Hardness: 2.5 – 3 Streak: Blackish lead-gray Density: Lustre: Dull metallic Habit: Chunky fracture, massive habit. Colours: Blackish lead-gray Crystal System: Monoclinic Cleavage: Indistinct Fracture: Conchoidal Magnetism: None Reaction with HCl: None Identification in hand sample: Black colour with sooty appearance on weathered surfaces and sectile character are distinctive. Bronze-yellow on fresh surfaces. Associations: Found in the supergene-enriched zone of copper-bearing hydrothermal sulfide deposits. Industrial / ecomonic uses: Mined as a source of copper. Sulfides

42 Chalcopyrite (CuFeS 2 ) Hardness: 3.5 – 4 Streak: Greenish black Density: Lustre: Metallic Habit: Fine grained to massive aggregates. Colours: Brass yellow, may be tarnished and iridescent. Crystal System: Tetragonal Cleavage: Poor Fracture: Conchoidal Magnetism: None Reaction with HCl: Very weak Identification in hand sample: Distinctive brassy-green colour. Has a richer yellow colour than pyrite and a lower hardness. Associations: Most common copper-bearing mineral, found in many hydrothermal sulfide deposits. Often associated with galena, sphalerite, pyrite and other sulfides. Industrial / ecomonic uses: Mined for its copper which has innumerable industrial uses. Sulfides

43 Galena (PbS) Hardness: 2.5 Streak: Lead gray Density: 7.6 Lustre: Metallic Habit: Excellent cubic cleavage, crystals usually very evident Colours: Lead gray Crystal System: Isometric Cleavage: Perfect cubic Fracture: Subconchoidal Magnetism: None Reaction with HCl: Weak Identification in hand sample: Gives off a rotten-egg smell in HCl, very high SG, very metallic lustre. Associations: Very common in hydrothermal sulfide deposits. Associated with sphalerite, pyrite, chalcopyrite, quartz, calcite, fluorite, and/or barite. Industrial / ecomonic uses: Main ore from which lead is extracted, also a source of silver. Sulfides

44 Pyrite (crystalline) FeS 2 Hardness: Density: 5.0 Lustre: Metallic Streak: Greenish/brownish black Habit: Perfect cubic crystalline habit. Colours: Bronze-yellow Crystal System: Isometric Cleavage: Good Fracture: Conchoidal Magnetism: Unknown Reaction with HCl: None Identification in hand sample: Colour, hardness, streak and habit are best indicators. Gives off sparks when struck with a hard metal object. Associations: Most common sulfide mineral, almost always present in hydrothermal deposits. Industrial / ecomonic uses: May be used as source of iron or sulfur, but not normally of economic value. Sulfides

45 Stibnite (Sb 2 S 3 ) Hardness: 2 Streak: Lead gray Density: Lustre: Metallic Habit: Range from fine to medium grains to prismatic crystals (with longitudinal striations). Complex terminations, radiating acicular groups. Colours: Lead gray, black, iridescent tarnish Crystal System: Orthorhombic Cleavage: Perfect Fracture: Subconchoidal Magnetism: None Reaction with HCl: Weak Identification in hand sample: Colour and small subhedral crystals are indicators. Also rather soft. Associations: Forms in low-temperature hydrothermal veins, or is deposited from hot mineral springs. Industrial / ecomonic uses: Important source of antimony (Sb) Sulfides

46 Copper (Cu) Hardness: Streak: Same Density: 8.9 Lustre: Metallic Habit: Massive, platey or dendritic habit. Colours: Light rose on fresh surface, copper-red on tarnished surface Crystal System: Isometric Cleavage: None Fracture: Hackly Magnetism: None Reaction with HCl: Weak Identification in hand sample: Colour and metallic characteristics are diagnostic. Associations: Found associated with mafic volcanic rocks, formed by reaction between Cu-bearing solutions and Fe- bearing minerals. Associated minerals are cuprite, chalcocite, bornite, epidote, calcite, chlorite and zeolites. Industrial / ecomonic uses: Used as electrical wire due to electrical conductivity and relatively low price. Comments: Obviously a source of copper, however most copper in modern times is mined from sulfide minerals. Native Elements

47 Graphite (C) Hardness: 1 – 2 Streak: Black Density: Lustre: Dull metallic, greasy feel Habit: Fine grained aggregate Colours: Silver-black Crystal System: Hexagonal Cleavage: Perfect basal Fracture: Uneven Magnetism: None Reaction with HCl: None Identification in hand sample: Softness and lustre are best indicators. Associations: Common in pelitic metamorphic rocks such as phyllite, slate and schist. Produced as a result of decomposition of organic material. Industrial / ecomonic uses: Used in pencil leads and as a dry lubricant. Comments: Due to its softness, graphite is usually quite messy! Native Elements

48 Cupit, Kerry. Mineral June2011. Online. Reference


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