Page 9 - Curriculum Visions Dynamic Book

 Ruby set in the greenstone rock (zoisite) in which it is normally found. The hexagonal crystal system
to which ruby belongs shows clearly in this example.
bond: chemical bonding is either a transfer or sharing
of electrons by two or more atoms. There are a number of types of chemical bond, some very strong (such as covalent bonds), others weak (such as hydrogen bonds). Chemical bonds form because the linked molecule is more stable than
Ruby the unlinked atoms from which it formed. For example,
the hydrogen molecule (H2) is more stable than single atoms
of hydrogen, which is why hydrogen gas is always found as molecules of two hydrogen atoms.
gemstone: a wide range of minerals valued by people, both as crystals (such as emerald) and as decorative stones (such as agate). There is no single chemical formula
for a gemstone.
molecule: a group of two or more atoms held together by chemical bonds.
 Sapphire is a pale blue to deep violet form of corundum (see also page 6). The colours are produced by various amounts of the elements iron and titanium.
Most transparent corundum is known as sapphire, except for the red varieties which are called ruby (see page 8). Consequently, rubies and sapphires are often collected
from the same deposits as the corundum that is used in industry. Sapphires can be made
artificially and are used where hard wearing is vital, such as for the
jewels of watch bearings. Sapphire can also be
used as an abrasive.
9
9