The unit cell of any substance will contain one or integral multiple of
chemical formula units (Z value). Mineral formulas are based on the relationship
to unit cell volume and the positions of atoms within the unit cell.
Calculation of Chemical Composition
The calculation of the chemical composition is straight-forward. The
molecular weight from the empirical formula divided by the sums of the atomic
weights of each element to yield the percentage of each element. This is done
for each element in the empirical formula and tabulated as the chemical
composition. Please note the sort order is based on the electro-negativity of
Additional information provided is the chemical composition expressed as the
% oxide of the element. These data are provided to help in the comparison of
mineral analyses which use oxide percent. The convention of reporting the oxide
percent dates back to when minerals and rocks were analyzed using wet-chemical
methods to precipitate an element. The precipitate was oxidized under high
temperature and the results were weighed as the oxide.
Since we have all this detailed chemical composition data, the following
search form will identify possible minerals by searching for 1 to 3 chemical
analysis. This is a great way to help identify unknown substances.
Mineral Element Composition Search - To Reset -
Other References on Chemical Composition
Search the Mineralogy Database
Example Subject Searches
Example: Use potassium sodium calcium for minerals that contain
those elements without regard to order of occurrence. Example: To find minerals containing Li, Ba, without Ca, try
+lithium +barium -calcium. (note: the "+" sign is optional, the "-" sign
is not) Example: Use copper-26 -"Dana Class-3" or -"Dana
Class-2" to find all non-sulfide minerals containing 26.00% to 26.99%
copper. Example: Use "Silver" "Gold-2*" to find all silver minerals
containing 20.0% to 29.99% gold.
The safest way to search for elements is to spell out the element name in
full since every page has a chemical composition. Be sure to use sulfur and not
sulfate since sulfate is not reported or analyzed. Use chlorine and not
chloride, carbon and not carbonate, etc.