The Building Blocks of Gemstones: Extra Notes

Ionic Bonding- bonding resulting from electrostatic attraction of negatively and positively charged anions and cations. Examples: peridot, topaz, garnet (note that the single silicate tetrahedra in these gems join together with ionic bonds, however the atoms in the tetrahedra usually have covalent bonds)   Covalent Bonding- bonding as a result of the sharing of outer shell electrons so as to obtain a suitable outer shell configuration in each atom. Examples: diamond, emerald, tourmaline, quartz   Metallic Bonding- in metallic bonding, the atoms are closely packed; electrons in the higher energy level shells are shared between several atoms and are so loosely held that that they can readily drift from one atom to another. Examples: gold, silver, platinum   Van der Waals Bonding- this bonding arises as a weak secondary attraction between certain molecules formed by the transfer or sharing of electrons. Examples: talc, soapstone   Atom- the smallest individual particle that retains the distinctive properties of a given chemical element.   Compound- a combination of atoms of one or more elements with atoms of another element in a specific ratio.   Molecule- the smallest unit that has all the properties of a particular compound.   Valency- the combining power of an ion; the number of electrons which the atom needs to lose or gain to obtain a stable outer shell.   Polymorphs- the ability of a specific chemical substance to crystallize with more than one type of structures known as polymorphi