Also rubellite is a variety of tourmaline - basically it is 'ruby-like' tourmaline. Indicolite is a blue variety of tourmaline but tourmaline basically comes in every colour imaginable - the most desirable is Pairaba tourmaline (think the colour of a swimming pool).
Morganite is a powder peachy-pink - the more colour saturation the better in terms of value.
Kunzite comes in a couple of colours (there are yellow and clear varieties) but is most often a pale true-pink. Again, the stronger the colour the better. It is also phosphorescent so when it has been in light and then goes into darkness it appears to glow.
Kyanite is found mostly in high mountains - nepal and the himalayas seem to be the richest source. It is a deep blue and looks like the best sapphire.
Sapphires are not all created equal - the most highly prized come from sri lanka (and are still referred to as cylon sapphires). However, Sapphires also come in lots of other colours - yellow, pink, green etc - and are referred to as 'fancy'. You can get sapphires from argos for £50 but they are almost black and therefore pretty crap!!
Colour change stones - you can get stones that seem to change colour according to the light they are viewed in. There are sapphires, garnets and other gems, such as alexandrite, that appear blue/green in one light and red/purple in another.
Zircon is not the same as cubic zirconia!! Zircon is a real gem that comes out of the ground and is beautiful - cheaper than diamonds and more fire than diamonds too. Cubic zirconia comes from a lab and is fake and horrible.
Amethyst and citrine come from the same family and there is a gem called ametrine where one half is amethyst and the other is citrine (one part of the earth was cold and the other was hot). This happens with quartz too and is regarded as a true phenomenon.
They are finding new gems all the time - a new gem was launched last year called astraeolite and it is clear (quartz I think) with specks of fools gold that look like stars - really pretty.