SILICATES CLASS:
The Silicates are the largest, the most interesting, and the most complicated class of minerals by far.
Approximately 30% of all minerals are silicates and some geologists estimate that 90% of the Earth's crust is made up of silicates.
With oxygen and silicon the two most abundant elements in the earth's crust, the abundance of silicates is no real surprise.
The basic chemical unit of silicates is the (SiO4) tetrahedron shaped anionic group with a negative four charge (-4). The central
silicon ion has a charge of positive four while each oxygen has a charge of negative two (-2) and thus each silicon-oxygen bond is
equal to one half (1/2) the total bond energy of oxygen. This condition leaves the oxygens with the option of bonding to another
silicon ion and therefore linking one (SiO4) tetrahedron to another and another, etc..
The complicated structures that these silicate tetrahedrons form is truly amazing.
They can form as single units, double units, chains, sheets, rings and framework structures. The different ways that the
silicate tetrahedrons combine is what makes the Silicate Class the largest,
the most interesting and the most complicated class of minerals.
|