Polymorf - Knowhwere- Minerals

Geometry and symmetry of minerals

The bulk of the matter comprising the earth's crust exists as compounds of

elements called minerals. There are more than 3,000 naturally occurring inorganic

minerals, many of which exist in solid forms of varying composition, not to mention

the countless number of synthetic compounds that have been formulated.

Conventional mineral classification scheme

Mineralogists have attempted to bring order to this vast collection of diverse matter

by cross indexing minerals with the chief nonmetal or radical present and the type of

structure commonly exhibited by them. Often elements and minerals grouped in this

way are very similar in appearance, behave similarly when treated chemically, and

occur under similar geologic conditions.

The following table is an example of such a classification scheme. In the left hand

column the elements and minerals are grouped by the chief non-metal or radical

present. In the right hand column each group is subdivided by the type of structure

commonly exhibited by the group. The name of the structure is derived from an

element or mineral of the subgroup that is most commonly identified with the

structure or exhibits it most clearly.

.
Element/mineral	Structural type	Element/mineral	Structure type
Native metals		Halides (continued)
Au,Ag,Cu,Pb,Pt,Pd	gold	halite group
a-Sn	diamond	halite	halite
a-Fe	bcc	sylvite	" "
Native nonmetals		fluorite	fluorite
C (diamond)	diamond	Oxides
C (graphite)	hp	periclase group
Sulfides		periclase	halite
cinnabar	zincblende	bunsenite	" "
greenocite	wurtzite	manganosite	" "
galena group		zincite group
galena	halite	zincite	wurtzite
altaite	" "	bromellite	" "
clausthalite	" "	cuprite	cuprite
albandite	" "	corundum group
oldhamite	" "	corundum	corundum
sphalerite group		hematite	" "
zincblende	zincblende	ilmenite	" "
metacinnabar	" "	spinel group
tiemannite	" "	spinel	spinel
coloradoite	" "	gahnite	" "
molybdenite group		hercynite	" "
molybdenite	molybdenite	magnetite	spinel (inverse)
tunstenite	" "	rutile group
argentite group		rutile	rutile
argentite	anti-flourite	pyrolusite	" "
chalcopyrite group		cassiterite	" "
chalcopyrite	zincblende	plattnerite	" "
stannite	" "	urraninite group
niccolite group		urraninite	flourite
niccolite	niccolite	thorianite	" "
pyrrhotite	" " (def.)	diaspore group
breithuptite	" "	diaspore	diaspore
skutterudite group		goethite	" "
skutterudite		brucite group
Sulfosalts		brucite	CdI₂
enargite group		pyrochroite	"
enargite	enargite	portlandite	"
Halides		boehmite
nantokite	zincblende	lepidocrocite	boehmite
marshite	" "	litharge	PbO
miersite	" "

Table 3 - Conventional mineral classification system

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