Definition
The empirical formula is derived from the mineral's structural (molecular) formula by using the published analysis of the mineral or deriving the analysis using basic rules.
1.Atomic substitutions were analyzed by the following procedure if published analyses were not available. Adjustments were made to match the measured density with the calculated density if needed:
(K,Na) = K 0.75 Na 0.25
(K,Na,Cs)= K 0.6 Na 0.3 Cs 0.1
2.Rare Earth Elements ( REE in formulae ) were calculated based on the chondrite normalized abundances. This database used 144 for the REE atomic weight and 61 as the atomic number.
3.Solid solution series minerals were calculated based on the mid-points of the accepted compositional range of the mineral.
The empirical formula was used to calculate the chemical composition in this database.