MINERALS

CHEMICAL COMPOSITION -

MOST IMPORTANT ARE SILICATE OR SiO2 -BEARING,

such as

QUARTZ - SiO2

OLIVINE (Mg,Fe)2SiO4

PYROXENE (enstatite) MgSiO3

FELDSPAR (albite) NaAlSi3O8

CAN HAVE RANGE OF COMPOSITIONS -

SOLID SOLUTION: OLIVINE (Mg,Fe)2SiO4 CAN RANGE FROM PURE Mg2SiO4 TO Fe2SiO4

CRYSTAL STRUCTURE -

HOW ATOMS ARE ARRANGED: ATOMS OF APPROPRIATE SIZE CAN FIT INTO PARTICULAR STRUCTURES

PHASE -

DIFFERENT STRUCTURES FOR SAME COMPOSITION DEPENDING ON TEMPERATURE AND PRESSURE