Chapter 8, Crystal Chemistry and systematic descriptions of Native Elements, sulfides, and sulfosalts.

I.                    Mineral classification

a.       Chemical composition – basis for classification of minerals

b.      Divided into classes depending on the dominant anion or anionic group

                                                               i.      Minerals in the same anionic group has similar characteristics

                                                             ii.      Better than cations

                                                            iii.      Tend to occur together or in the same geological environment.

c.       Also based on internal structure (thanks to x-ray)

d.      For the purpose of this book, we will use these groups

                                                               i.      Chapter 8

1.      native elements

2.      Sulfides

3.      Sulfosalts

                                                             ii.      Chapter 9

1.      Oxides

                                                            iii.      Chapter 10

1.      Halides

2.      Carbonates

3.      Nitrates

4.      Borates

5.      Phosphates

6.      Sulfates

7.      Tungstates

                                                           iv.      Chapter 11

1.      Silicates

2.      Based on structures

II.                 Crystal Chemistry of Native Elements, Sulfides, and Sulfosalts

a.       Native Elements

                                                               i.      Except for the free gases, there are only about 20 elements that occur in a native state

1.      Metals

a.       Very simple structures,

b.      Three groups,

                                                                                                                                       i.      Gold – gold, silver, copper, lead: all isometric

1.      isostructural, face centered cubic lattice

2.      soft, malleable, ductile and sectile, excellent conductors of heat and electricity, metallic luster and hackly fracture and low melting points.

                                                                                                                                     ii.      Platinum – platinum, iridium and osmium, higher melting points and harder

                                                                                                                                    iii.      Iron – iron, nickel: cubic packing and iron often replaces iron as they are similar in size.

2.      Semimetals – arsenic, antimony and bismuth and selenium and tellurium:  Covalent nature develops more of a pyramid that close packing of spheres, lower symmetry

3.      Nonmetals – sulfur and carbon:  Sulfur can be orthorhombic or monoclinic based on the formation conditions, carbon in graphite is sheet like in structure while diamonds are more pyramid shaped.  Diamond is a super conductor of electricity and heat. 

b.      Sulfides

                                                               i.      Sulfur is the anion bonded to a metal

                                                             ii.      Most or opaque or translucent and distinctive color and streak

c.       Sulfosalts

                                                               i.      Unoxydized sulfur mineral, double sulfides

                                                             ii.      Occur as minor minerals I hydrothermal veins associated with the more common sulfides.