Silicon Tetrahedra by Charina Cameron4 oxygen atoms1 silicon atom in the centerForms a 4-sided geometryEach side is like an equilateral triangleCreates a 4- ion

Some Silicate structuresSingle tetrahedrons, single chains, double chains, sheets, rings, and 3-D networks

SINGLE SILICATE TETRAHEDRAGarnet (red)

Olivine (green)(Fe,Mg)SiO4crystal

SINGLE CHAIN SILICATESPyroxene Group [Fe,Mg,Ca,Al silicates]:Augite (note the near 90o angle of the two cleavages)

DOUBLE CHAIN SILICATESAmphibole Group [Na,Ca,Fe,Mg,Al silicates w/ H2O]:The mineral hornblende is commonNnote the 156 degree angle of the two cleavages

SHEET SILICATESMuscovite mica [K,Al + H2O] Biotite mica [K,Mg,Fe,Al + H2O]Note the single perfect cleavage and elastic sheets

TalcKaolinite (clay)[K,Al + H2O]

ZEOLITE RING SILICATESNaturalite from North Mountain Basalt Formation

FRAMEWORK SILICATESFeldspar group:Most abundant mineral groupOrthoclase (K-feldspar)

Albite (Na-Plagioclase)

Labradorite (Ca-rich Plagioclase)2 cleavagesnote twinning lines

FRAMEWORK SILICATESQuartz (SiO2), the most common mineral:

Chalcedony (SiO2):microcrystalline quartzmany var. (chert, jasper, flint)amethystquartz crystalmilky quartzrose quartz

FRAMEWORK SILICATESHexagonal quartz crystal

FRAMEWORK SILICATESAmethyst (quartz) geode from the Scots Bay Formation

FRAMEWORK SILICATESAmethyst (quartz) geode replacing small straight tree trunk surrounded by chert (from Scots Bay Fm)