This is how we classify minerals! Silicates and Non-Silicates

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1 Why are some minerals harder than others? Their atomic structure and chemical formula. This is how we classify minerals! Silicates and Non-Silicates

2 Part #1 - Silicates: Silicon and Oxygen make up 70% of the earth s crust and are therefore the two most common elements. The largest group of minerals, therefore, is the SILICATE GROUP: all of which are compounds containing silicon and oxygen along with various other elements.

3 Percentages of Elements in Earth's Crust

4 Silica Tetrahedron: Tetrahedron: The basic unit of all silicates. Formed by ONE Silicon Atom surrounded by FOUR Oxygen Atoms. Shaped Like a Pyramid

5 1 Silicon Oxygen 4

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7 The Silicates are subdivided on basis of crystal structure: In other words the ways in which the Silicon-Oxygen Tetrahedra are linked together!

8 STRUCTURAL GROUPING OF THE SILICATE MINERALS: BASED ON HOW SILICON-OXYGEN TETRAHEDRA ARE ARRANGED! FrameWork Silicates - (Basically a 3D tightly packed mass of Tetrahedra) Tend to be very HARD & resistant to weathering!! Sheets - Chains Of Tetrahedra - Isolated Tetrahedra - Feldspars*** Most Common Mineral On Earth!! Compose About 60% of the Earth s Crust Quartz** Second Most Common Mineral On Earth!! Micas* Biotite = Brown Muscovite = White Chlorites Clays Pyroxene = Single Chain AKA Augite Amphibole = Double Chain AKA Hornblende Olivine Garnet Increasing Structural Complexity

9 Isolated Tetrahedra: The simplest arrangement of Tetrahedra. OLIVINE & GARNET. Ionic bonding with Magnesium or Iron Glassy looking, pale green Found in oceanic crust and upper mantle

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11 Olivine

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13 Another common single tetrahedron silicate is GARNET. SiO4 tetrahedrons bonded to Magnesium, Iron, Calcium, or Manganese. Reddy brown to black in colour. Found in continental crust. Commonly form crystals

14 CHAIN SILICATES: Other silicates have their Tetrahedra arranged in chains. Formed by the sharing of Oxygen atoms between adjacent Tetrahedra in one dimension. Two Types - single chains and double chains

15 Single chain structure in pyroxenes Double chain structure in amphiboles

16 Single-chain Silicates- One large group of single-chain silicates is collectively known as PYROXENES. PYROXENE is also called AUGITE Ionic bonding of SiO4 tetrahedrons with Calcium and Magnesium single chains. Shiny black in color, and luster Found in oceanic crust and mantle

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19 Double-chain silicates- Known as AMPHIBOLES. A common AMPHIBOLE is HORNBLENDE: (Ca,Na)3(Mg,Fe,Al,Ti)5(Si,Al)8O22(OH,F)2 Ionic bonding of SiO4 tetrahedrons with Calcium, Magnesium, and Hydroxides Dark green to black in color

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21 Sheet Silicates: Tetrahedra are linked by shared Oxygen atoms in 2 dimensions. MICAS are a compositionally diverse group of sheet silicates that have in common excellent cleavage parallel to weakly bonded sheets of Tetrahedra

22 Sheet Arrangement of Tetrahedra

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24 MICAS: MUSCOTIVE often found in granite, colorless (clear) BIOTITE rich in iron and magnesium giving it a dark brown-black color

25 CHLORITE: usually green in color CLAY MINERALS are also sheet silicates and their slippery feeling can be attributed to the sliding apart of such sheets of atoms Earthly smell Example: Kaolinite, which is white in color

26 Framework Silicates: Tetrahedra are firmly linked in all 3 dimensions by shared Oxygen atoms. Basically a tightly packed mass of Tetrahedra. Tend to be very HARD and resistant to weathering & therefore VERY COMMON!!

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28 Feldspars: Most common mineral on earth!! 60% of Earth s crust... Two types: Potassium Feldspar or K-SPAR or Orthoclase Contains K potassium. Pinkish in colour Plagioclase: traces of sodium, calcium, or both in their structure Whitish in colour

29 Quartz: Second most common mineral on Earth. Framework exists entirely of Silicon-Oxygen Tetrahedra, the net charge on each is 0. 0 impurities. Only mineral to exhibit this type of structure. Found extensively in continental crust Colour can vary from white to black

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34 Silicates Summary: ISOLATED TETRAHEDRA Olivine Garnet CHAIN SILICATES Pyroxene (Augite) (SINGLE) Amphibole (Hornblende) (DOUBLE) SHEETS Micas Clays Chlorites FRAMEWORK SILICATES Feldspars (most common, 60% of Earth s crust) Quartz (second most common mineral)

35 Part #2 - Nonsilicates: Each Nonsilicate Mineral group is defined by some chemical characteristic that all members of the group have in common.

36 NONSILICATES: 1. Carbonates 2. Halides 3. Native elements 4. Oxides 5. Sulfides 6. Sulfates

37 CARBONATES: Chemical formulas all contain the Carbonate Group (CO3) Are not made of SiO4 Tetrahedra! Not as common as silicate minerals but usually more valuable economically Carbonate minerals dissolve easily, particularly in acids said to Effervesce! Oceans contain a great deal of dissolved carbonate

38 Most important carbonate mineral is CALCITE (CaCO3)

39 DOLOMITE is another common carbonate mineral Contains calcium and magnesium (CaMg(CO3)2)

40 HALIDES: Structure includes chlorine or fluorine combined with sodium, potassium or calcium Example: Fluorite (CaF2) or Halite (NaCl)

41 Fluorite

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43 NATIVE ELEMENTS: Minerals that are each made up of a single chemical element. Structure is a pure substance of only one element. Minerals name is usually same as names of corresponding elements. Ex) Gold, Silver, Platinum, Copper, Sulfur Etc. Ex) Diamond and Graphite are both examples of native carbon

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45 Native gold

46 Native silver

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48 Native Copper

49 OXIDES: Minerals that contain just one or more metals combined with oxygen and that lack the other elements necessary for them to be classified as silicates, sulfates, carbonates, etc. Structure includes oxygen and anther element which cannot be silicon Magnetite (Fe3O4) Corundum (Al2O3) Hematite (Fe2O3)

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51 SULFIDES: When sulfur is present without oxygen. Usually heavy dense metallic minerals.

52 Examples: Iron sulfide = PYRITE (FeS2) Also called fool s gold Metallic golden color Lead sulfide = GALENA (PbS) Forms in silver colored cubes Zinc Sulfide = SPHALERITE (ZnS)

53 Pyrite

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55 Sphalerite

56 SULFATES: All contain the Sulfate Group (SO4). sulfur WITH oxygen! The calcium sulfate GYPSUM is most important Abundant Commercially useful Sulfates of other elements are also found: barium, lead, strontium for example.

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58 CARBONATES Carbonate group (CO3) Calcite, dolomite Nonsilicates Summary: HALIDES Chlorine/fluorine combined with sodium, potassium or calcium Halite, fluorite NATIVE ELEMENTS Pure substance of one element Gold, silver, copper OXIDES Oxygen and another element which cannot be silicon Magnetite, corundum, hematite SULFIDES One or more elements combined with sulfur Sphalerite, pyrite, galena SULFATES Sulfate group (SO4) Gypsum