Mineral Formulas & Compositions

A big part of being able to understand mineral processes, and to think intelligently about rocks you come across is to understand the mineral compositions. For example, you might not be able to identify a mineral in a rock conclusively without lab tests (say, talc vs. pyrophyllite), but by knowing the other minerals in the rock and their compositions, you can make a good guess in the field (because phlogopite is present, it's probably talc, since both phlogopite and talc have Mg).

By the final exam, you should know the compositions and/or formulas for these minerals. For those in which you are to know compositions only, I want you to know which elements or ions are in the structure, but not necessarily the relative amounts of each. For all the minerals you should also know the chemical group (e.g., borate, silicate, sulfide), the mineral group if it is a member of one (e.g., magnetite is a spinel, forsterite is an olivine, phlogopite is a biotite). For the silicates, you should also know the structural group (quartz is a framework silicate).

Mineral Identification

Of course, a big part of the course is learning to identify minerals. You must be able to identify all the minerals on the list below in "hand specimen," using only the standard tools (streak plate, scratch kit, acid, hand lens & your eyes/brain. For the most common rock-forming minerals, and a few others, you should also be able to identify them in thin section - these are indicated below.

Mineral Learn composition only? Identify in thin section   Mineral Learn composition only? Identify in thin section
Graphite
  Staurolite
Yes
Yes
Sulfur
  Titanite
Chalcocite
  Epidote
Yes
Bornite
  Vesuvianite
Yes
Galena
  Beryl
Sphalerite
  Tourmaline
Yes
Yes
Chalcopyrite
  Enstatite
Stibnite
  Diopside
Pyrite
  Augite
Yes
Yes
Molybdenite
  Jadeite
Corundum
  Wollastonite
Hematite
  Tremolite
Yes
Ilmenite
  Actinolite
Yes
Magnetite
  Hornblende
Yes
Yes
Rutile
  Glaucophane
Chromite
  Serpentine
Yes
Goethite
  Kaolinite
Yes
Halite
  Talc
Fluorite
Yes
  Muscovite
Yes
Calcite
Yes
  Lepidolite
Yes
Siderite
  Biotite
Yes
Aragonite
  Chlorite
Yes
Yes
Dolomite
  Quartz
Yes
Malachite
Yes
  Cristobalite
Azurite
Yes
  Opal
Barite
  Microcline
Yes
Gypsum
  Orthoclase
Yes
Forsterite
Yes
  Sanidine
Yes
Almandine
Yes
  Plagioclase
Yes
Grossular
  Leucite
Yes
Zircon
Yes
  Sodalite
Yes
Andalusite
  Stilbite
Yes
Sillimanite
 
Kyanite
 
Topaz
Yes
 


David M. Hirsch
Modified on Mon, Jul 12, 2004 at 11:14 PM