Chemistry of Minerals
It is possible to write a chemical formula to express the composition of a mineral, and such formulae are used as a short way of expressing mineral chemistry. Atoms can conveniently be regarded as electrically neutral because the positive charge on the nucleus is balanced by the negative charges of the surrounding electrons. Atoms can, however, gain or lose one or more electrons and so become either negatively or positively charged, when they are called ions. Negatively charged ions are called anions and positive ions are called cations. A chemical compound can be regarded as being made up of two parts, a positively charged cationic part and a negatively charged or anionic part. The resulting compound is electrically neutral because the two sets of charges are in balance. The positive part is usually a metal and is always the first part of a written chemical formula. The negative or anionic part of the formula can be either a nonmetallic ion such as oxygen or sulfur or else a combination of several elements to form a negatively charged group, such as carbonate (CO3) or sulfate (SO4). The table below lists the chemical symbols of the elements referred to in this book.
Ag Silver
Al Aluminum
As Arsenic
Au Gold
B Boron
Ba Barium
Be Beryllium
Bi Bismuth
Bi Bismuth
C Carbon
Ca Calcium
Cd Cadmium
Ce Cerium
Cl Chlorine
Co Cobalt
Cr Chromium
Cu Copper
F Fluorine
F Fluorine
Fe2+, Fe3+ Iron
H Hydrogen
Hg Mercury
K Potassium
La Lanthanum
Li Lithium
Mg Magnesium
Mg Magnesium
Mn2+, MN3+, Mn4+ Manganese
Mo Molybdenum
N Nitrogen
Na Sodium
Nb Niobium
Ni Nickel
O Oxygen
P Phosphorus
Pb Lead
S Sulfur
Sb Antimony
Si Silicon
Sn Tin
Sr Strontium
Ta Tantalum
Th Thorium
Ti Titanium
U Uranium
V Vanadium
W Tungsten
Y Yttrium
Zn Zinc
Zp Zircenium
Some common anionic groups and their names are given below.
Al2O4 etc Aluminate
As, As2 etc Arsenide
AsO4 etc Arsenate
BO3, B3O4 etc Borate
Cl, Cl2 etc Chloride
CO3 Carbonate
CrO4 etc Cromate
F, F2 etc Fluoride
MoO4 etc Molybdate
N, N2 etc Nitrate
NO3 Nitrate
NbO3 etc Niobate
O, O2 Oxide
OH, (OH)2 etc Hydroxide
PO4 etc Phosphate
S, S2 etc Sulfide
SiO4, Si2O7 etc Silicate
SO4 Sulfate
TaO3 etc Tantalate
TiO3 etc Titanate
UO2 etc Uranate
VO4 etc Vanadate
WO4 etc Tungstate
In chemical formulae the subscript numerals denote the numbers of atoms of the preceding element that are present in the formula unit. When referring to a chemical compound by name it is simply necessary to state, in turn, the cationic and then the anionic part that follows; for example, CaCO3 is calcium carbonate, FeS2 is iron sulfide, CaF2 is calcium fluoride, (Mg,Fe)SiO4 is magnesium (or) iron silicate, and so on. By contrast KAlSi3O8 is potassium aluminum silicate, or better, potassium aluminosilicate; here there are two parts of the cationic group and they are emphasized in the way shown. Another example is K2(UO2)2(VO4)23H2O which is called hydrated potassium uranylvanadate. Notice that water of crystallization (H2O) is referred to by the adjective ‘hydrated’. Atoms which can substitute one for the other in a mineral are written so (Mg,Fe).
Question: What minerals, on loan from the San Bernardino County Museum, are on display at the Needles Regional Museum? Prepare a list of them, get there chemical formulae, and group them by anionic group. Note especially silicates. Have C. More and others contribute a display of minerals collected in the Tri-State.
Question: What minerals, on loan from the San Bernardino County Museum, are on display at the Needles Regional Museum? Prepare a list of them, get there chemical formulae, and group them by anionic group. Note especially silicates. Have C. More and others contribute a display of minerals collected in the Tri-State.
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