Crystal structure model - garnet

G Menzer of Berlin reported the crystal structure of garnet in its six major forms in 1928.

The general chemical formula of garnet is MIII MII (SiO4)3 and it an orthosilicate mineral. In pyrope, the garnet most in jewellery the divalent metal (MII) is magnesium and the trivalent metal (MIII) is aluminium. The ball and spoke model shows the structure of the unit cell, oxygen being represented by red, and silicon by black. The model represents pyrope if magnesium is represented by silver having six adjacent oxygen atoms, and aluminium is represented by gold with eight adjacent oxygens.

This structure, containing eight molecules or 160 atoms (cf of sodium chloride with four molecules or 8 atoms per unity cell) is evidence of the rapidly growing power of X-ray crystallography.