Figure 3.6: One silicon atom bonds to four oxygen atoms to form the building block of
silicate minerals. ( 15 )
Notice that the silicon and oxygen form a shape like a pyramid; this is the tetrahedron.
The pyramid-shaped building blocks can combine together in numerous ways. The silicate
mineral group is divided into six smaller groups, which are determined by the way the silicon-
oxygen building blocks join together. The pyramids can stand alone, form into connected
circles called rings, link into single and double chains, form large flat sheets of pyramids or
join in three dimensions.
Feldspar and quartz are the two most common silicate minerals. Beryl is a silicate mineral,
which forms rings from the tetrahedra. The gemstone emerald is a type of beryl that is
green because of chemical impurities. Biotite is a mica, which is another silicate mineral
that can be broken apart into thin, flexible sheets. Compare the beryl and the biotite shown
inFigure3.7.
Figure 3.7: Beryl and biotite are both silicate minerals. ( 6 )