MINERALS TYPES OF BONDING INTERMOLECULAR BONDING HYDROGEN BONDING Occurs primarily between water molecules due to polarity. VAN DER WAALS BONDING Occurs when all electrons end up on one side of atoms and a charge develops. Carbon in Graphite
MINERALS DETERMINANTS IN MINERAL FORMATION The minerals that form in the Earth are dependent upon: abundance of available elements at time of formation. size of the elements. temperature and pressure at time of formation.
Most Abundant Elements in Earth’s Continental Crust ELEMENT PROPORTION OF CRUST’S WEIGHT (%) Oxygen (O) 45.20 Silicon (Si) 27.20 Aluminum (Al) 8.00 Iron (Fe) 5.80 Calcium (Ca) 5.06 Magnesium (Mg) 2.77 Sodium (Na) 2.32 Potassium (K) 1.68 98.03 All Other Elements 1.97 Total 100 % Most minerals in Crust are oxygen-silicon based compounds.
Most Abundant Elements in Entire Earth ELEMENT PROPORTION OF EARTH’S WEIGHT (%) Iron (Fe) 34.80 Oxygen (O) 29.30 Silicon (Si) 14.70 Magnesium (Mg) 11.30 Sulfur (S) 3.30 Nickel (Ni) 2.40 Calcium (Ca) 1.40 Aluminum (Al) 1.40 98.40 All Other Elements 1.60 Total 100 % Most minerals in Upper Mantle are oxygen-silicon-magnesium- iron compounds.
MINERALS Size of elements is also a factor in mineral formation. Positive ions are usually smaller than negative ions. Smaller positive ions tend to fit in spaces between larger negative ions.
MINERALS COMMON MINERAL GROUPS Rock forming minerals compose the most common rocks in the Earth’s crust and mantle. Seven basic mineral groups. Most of the minerals in the crust and mantle are silicates.
MINERALS NONSILICATE MINERALS NATIVE ELEMENTS Elements are generally solitary (homogeneous). Do not combine with other elements in nature. Gold (Au) Silver (Ag) Platinum (Pt) Diamond (C) Graphite (C) Sulfur (S) Copper (Cu) Gold Copper Silver
MINERALS NONSILICATE MINERALS CARBONATES Carbonate ion (CO32-) is prominent in minerals. Has -2 charge. Combines readily with positive ions. Bonds generally weak. Minerals are soft (3-4). Minerals are soluble in acidic water. Leads to cave development. Calcite (CaCO3) Dolomite (CaMg(CO3)2) CALCITE DOLOMITE
MINERALS NONSILICATE MINERALS OXIDES CORUNDUM Produced when negative OXYGEN (O2-) ions combine with positive metallic ions. Specular hematite (Fe2O3) Oolitic hematite (Fe2O3) Magnetite (Fe3O4) Corundum (Al2O3) SPECULAR HEMATITE OOLITIC HEMATITE MAGNETITE
MINERALS NONSILICATE MINERALS HYDROXIDES Produced when negative HYDROXIDE (OH-) ions combine with positive metallic ions. Limonite (FeOOH) Bauxite LIMONITE BAUXITE
MINERALS NONSILICATE MINERALS SULFIDES Produced when negative SULFUR (S2-) ions combine with positive metallic ions. Oxygen’s ugly sibling. Pyrite (FeS2) Chalcopyrite (Cu,FeS2) Galena (PbS) Sphalerite (Zn,Fe)S PYRITE GALENA CHALCOPYRITE SPHALERITE
MINERALS NONSILICATE MINERALS SULFATES Produced when negative SULFATE (SO42-) ions combine with positive metallic ions. Gypsum (CaSO4 . H2O)
MINERALS NONSILICATE MINERALS HALIDES Produced when negative HALIDE (F, Cl, Br, I) ions combine with positive metallic ions. Halite (NaCl) Fluorite (CaF2) HALITE FLUORITE
MINERALS SILICATES AND THEIR STRUCTURE Silicate minerals: Constitute 90% of the weight of the crust. Are a dominant constituent in igneous, metamorphic, and sedimentary rocks. Silicate crystal structure is a repeated grouping of four oxygen ions and one silicon ion. SiO4 Produces a silicon-oxygen TETRAHEDRON.
MINERALS SILICATES AND THEIR STRUCTURE Silicon tetrahedron (SiO4) produced a -4 charge. Allows bonding with other elements or other tetrahedra. Silicon-Oxygen Ratio Number of O ions shared by tetrahedra. A tetrahedron that shares none of its oxygen has Si:O ratio of 1-4. A tetrahedron that shares all of its oxygen has Si:O ratio of 1-2.
MINERALS FIVE PRINCIPLE SILICATE STRUCTURES 1. INDEPENDENT TETRAHEDRA - ISLAND SILICATES Independent tetrahedra have -4 charge. Tetrahedra bond with positive ions. Share no oxygen ions. Generally are hard minerals. Strong ionic bonding exists. Si:O ratio = 1:4 OLIVINE OLIVINE STAUROLITE GARNET
MINERALS 2. SINGLE CHAIN SILICATES Silica tetrahedra share two corner oxygen ions. Bonds with positive ions. Bonds within chains are strong. Bonds between chains are weak. Minerals cleave parallel to chains. Si:O ratio = 1:3 AUGITE Acquires Ca2+, Mg2+, Fe2+ to neutralize ionic charges.
MINERALS 3. DOUBLE CHAIN SILICATES Tetrahedra share two corners in linear chain and some share a third oxygen with tetrahedra in neighboring chain. Shared oxygen ions bond chains together. Si:O ratio = 1:2.75 Generally accept Na+, Ca2+, Mg2+, Fe2+, Al3+. ACTINOLITE HORNBLENDE
MINERALS 4. SHEET SILICATES Tetrahedra share 3 basal oxygen ions. Produces a sheet. Fourth oxygen bonds with positive ions. This bonds the sheet together. Bonds between the sheets are extremely weak. Si:O ratio = 1:2.5 MUSCOVITE BIOTITE
MINERALS 5. FRAMEWORK SILICATES Tetrahedra share all four oxygen ions with adjacent tetrahedra. Produces three-dimensional framework. Si:O ratio = 1:2 Quartz and relatives and Feldspars two most abundant mineral groups in the Earth’s crust.
FELDSPAR Two groups: Plagioclase feldspar contains Na and Ca Orthoclase feldspar contains K All have 2 directions of cleavage at 90. Most common mineral group in Earth’s crust QUARTZ (SiO2) Has extremely strong bonds Hardest of the common rock-forming minerals Has no cleavage, conchoidal fracture Quartz and relatives second most abundant mineral group in Earth’s crust.