Minerals Pt. 2

Minerals 1. Physical properties of minerals 2. Mineral groups

Building Blocks Of Minerals What is a Mineral? A naturally occurring inorganic solid with a definite chemical composition and molecular structure. Minerals can consist of elements or compounds. Majority are compounds. Example Galena (PbS) and Pyrite (FeS2) Native Minerals consist of only one type of element. Examples include Gold, Silver, Sulfur, Diamond, Copper. To be a mineral a substance must satisfy the following: 1) Occur in nature 4) Definite chemical composition 2) Inorganic 5) Definite molecular structure 3) Solid

Building Blocks Of Minerals What materials make up minerals? Elements: Names and Symbols of elements found in common minerals include: 1) Chlorine (Cl) 2) Calcium (Ca) 3) Carbon (C) 4) Aluminum (Al) 5) Copper (Cu) 6) Cobalt (Co) 7) Fluorine (F) 8) Gold (Au) 9) Hydrogen (H) 10) Iron (Fe) 11) Lead (Pb) 12) Magnesium (Mg) 13) Oxygen (O) 14) Nitrogen (N) 15) Nickel (Ni) 16) Manganese (Mn) 17) Silicon (Si) 18) Sodium (Na) 19) Silver (Ag) 20) Potassium (K) 21) Sulfur (S) 22) Tin (Sn) 23) Zinc (Zn) For Example: Halite – NaCl, Galena – PbS, Hematite - Fe2O3

Mineral Groups in the Earth’s Crust 7 main mineral groups are: Silicates (Si + O) Carbonates (C + O) Sulfates (S + O) Oxides (metal + O) Halides (metal + halogen) Sulfides (metal + S) Native elements (Consist of only one type of element. Examples: Gold, Silver, Sulfur, Diamond, Copper)

The two most abundant elements: Silicon (Si) Oxygen (O) Over 4000 minerals, but only a few dozen are considered rock forming minerals. Only 8 elements make up most of crust’s minerals & represent over 98% of the continental crust Ottawa Senators Are Insane, Calgary Should Play Montreal Oxygen, Silicon, Aluminum, Iron, Calcium, Potassium, Magnesium The two most abundant elements: Silicon (Si) Oxygen (O)

Average composition of the continental crust Mineral groups Percent of elements by WEIGHT Average composition of the continental crust

Average composition of the continental crust Mineral groups Percent of elements by VOLUME Average composition of the continental crust

Mineral groups Light colored (crust, esp. continental crust) Most Common Minerals Light colored (crust, esp. continental crust) Quartz (SiO2) - commonly transparent Feldspar (Si, O, Al, K, Na, Ca) - mostly white or pink Clay (same stuff as feldspar, with water) Calcite (CaCO3, shells) limestone - make cement Dark colored (mantle and oceanic crust) Olivine (Si, O, Fe, Mg, Ca) Earth’s Crust mostly Si, O

Mineral Group #1: Silicates The building block of all silicates is the silicon-oxygen tetrahedron SiO4 Two different views of this arrangement: silicon atom oxygen atoms

SiO SiO O Si electric charges of tetrahedra ions: 1 silicon (Si) atom 4 oxygen (O) atoms Si 4+ O 2- SiO 4 Silicon tetrahedron has charge of -4 SiO 4 4-

Every silicate mineral contains the elements silicon (Si) + oxygen (O) Most silicates combine with other elements (i.e. positively charged cations) to make a stable structure.

Silicates aren’t electrically neutral They’re neutralized by certain metallic ions, such as: iron (Fe) magnesium (Mg) potassium (K) sodium (Na) aluminum (Al) calcium (Ca)

Mineral groups The silicates

Tetrahedra can join: A single tetrahedron Two tetrahedra joined by a common oxygen atom

Sialic Silicates Simatic silicates Because silicates make up about 96% of the earths crust, it has been subdivided into TWO groups: Sialic Silicates Simatic silicates

Sialic Silicates rich in silicon and aluminum. main rock type found in continents and comprise about 85% of the crust. mineral are light in color Examples: Muscovite has a pearly lustre

Muscovite

Simatic Silicates rich in silicon and magnesium. main rock type found in the ocean floor and comprise less than 15% of the crust. mineral are dark in color Example: Olivine, pyroxenes, hornblende, biotite, garnet

Olivine Biotite Hornblende Garnet

Carbonates- contain the carbonate molecule CO3 Mineral groups Important Nonsilicate Minerals Carbonates- contain the carbonate molecule CO3 Calcite (CaCO3) Dolomite (CaMg(CO3)2  found together in sedimentary rock limestone,  Main ingredient to cement, roads & building stones

Mineral groups Important Nonsilicate Minerals Oxides compounds consisting of an atomic structure of oxygen combined with one or more metals. Hematite (Fe2O3) Bauxite (Al2O3), -> steel Sulfides- compounds consisting of an atomic structure of one or more metals combined with sulfur. Examples: Pyrite (FeS2), Galena (PbS), Sphalerite (ZnS).

Mineral groups Important Nonsilicate Minerals Halides- compounds consisting of an atomic structure of chlorine(Cl) or fluorine(F) with sodium(Na), potassium(K), or calcium(Ca). Ex: Halite (NaCl) -> common table salt Sulfates compounds consisting of an atomic structure of one sulfur and four oxygen (SO4). Ex: Gypsum (CaSO4 .H2O) -> main ingredient of plaster & other building materials

Native Minerals- elements that occur uncombined in nature. Mineral groups Important Nonsilicate Minerals Native Minerals- elements that occur uncombined in nature. commonly called native elements. Examples: Gold (Au), Silver (Ag), Copper (Cu), & Sulfur (S)

Hints to Classify Mineral Groups Olivine (Mg,Fe)2SiO4 Barite BaSO4 Calcite CaCO3 Mineral groups that end with “ate” and have an oxygen group in its chemical formula are one of the following; Silicates = Si + Ox Sulfates = S + Ox Carbonates = C + Ox

Hints to Classify Mineral Groups Hematite Fe2O3 Pyrite FeS2 Fluorite CaF2 Mineral groups that end with “ide” and have a metal (eg. Na, K) in its chemical formula are one of the following; Oxidides = Metal + O Sulfides = Metal + S Halides = Metal + Cl, Br, F

Physical properties of minerals We use physical properties of minerals to identify them Crystal form Luster Color Hardness Cleavage Fracture Specific gravity Taste Elasticity Feel Magnetization Optical properties Smell Streak

The properties of each mineral depends on the following; Physical properties of minerals The properties of each mineral depends on the following; 1) The type of elements present 2) The arrangement of atoms 3) The strength of bonding

Quartz (SiO2) Crystal form Shape of a crystal can reflect the orderly internal arrangement of atoms Quartz (SiO2)

Crystal form Shape of a crystal can reflect the orderly internal arrangement of atoms

The sooth flat surfaces on crystals are called faces. Crystal form The sooth flat surfaces on crystals are called faces. Shape of a crystal can reflect the orderly internal arrangement of atoms

The appearance of the mineral in reflected light. Luster The appearance of the mineral in reflected light. A metallic looking mineral: metallic luster Others: nonmetallic luster Ex: pearly, silky, glassy, adamantine, greasy, earthy.

Metallic Luster

Non-metallic Glassy Luster B) Greasy A) Glassy

D) Pearly C) Earthy . or Dull

One mineral can come in many colors. Obvious, but often misleading. Slight impurities in a mineral can change its color. Problems: One mineral can come in many colors. Different minerals can have the same color. Surface oxidation can change a minerals color.

Color Quartz (when pure it is colorless):

Various blue minerals

Surface Oxidation

Streak The true color of the mineral in its powdered form. To find the streak of a mineral, you perform a streak test. To do this you scratch a mineral across an unglazed porcelain tile and the powder streak left on the tile is the true color of the mineral.

Hardness- The resistance of a mineral to scratching.

Hardness is expressed in terms of Moh’s Hardness Scale which ranks relative hardness from 1 – 10.

If the object scratches the mineral then it is harder than the mineral.

Calcite Mica (sheets) Cleavage Tendency of a mineral to break along weak planes of bonding in crystal structure (some bonds are stronger than others) Calcite Mica (sheets)

Cleavage Cleavage directions are determined by atomic structure and strength of bonding.

Cleavage Cleavage follows areas of weak bonding.

Cleavage Plane Directions Minerals show cleavage in many different directions, but most common are in planes of one, two, and three directions. Cleavage in one direction (Basal Cleavage). Example: Mica displays this type of cleavage.

Cleavage Plane Directions Cleavage in two directions. Example: Orthoclase feldspar displays this type of cleavage.

Cleavage Plane Directions Cleavage in three directions. Example: Halite displays this type of cleavage.

Tendency of a mineral to break irregularly. Fracture Tendency of a mineral to break irregularly. Conchoidal Fracture is a curved breakage that resembles the concentric shape of a mussel shell. It often occurs in fine-grained minerals or in crystalline minerals

Specific gravity is the mass of a mineral compared to that of an equal volume of water 1.) weigh the specimen in air and record the weight.

2.) weigh the specimen submerged in water and record the weight. 3.) calculate specific gravity (S.G.) using the following formula. Specific Gravity = weight in air . weight in air - weight in water

Specific Gravity = Density Because pure water at 4EC has a density of 1 g/cm3, the specific gravity is equal to its density. Thus; Specific gravity = Density. Metric system 1ml = 1gram= 1 cm3 To determine Density you need to: 1) Use a scale to measure the mass of the mineral sample. 2) Find the volume of the mineral sample. 3) Calculate density (which equals specific gravity). Density = Mass(mineral) Volume(mineral) = Specific Gravity

Specific Gravity Given: 1mL = 1cm3 = 1g, we know the weight of an equal volume of water in grams. We can then use the following formula to calculate Specific Gravity: Calculation S.G. = W(mineral) W(water)

Other Properties Taste Elasticity Feel Magnetization Optical properties Smell Acid test Double refraction Fluorescence Acid Test - drop acid on the sample to see if the mineral reacts (fizzes). used to test the Carbonate group. Ex. Calcite (Limestone)