Well, to start with, there are two kinds of Jade: their geological names are Jadeite and Nephrite. The common names for Nephrite are Greenstone or in Maori - Pounamu.

Jadeite is found in an area around the northern Burnese border with China. Nephrite is found in New Zealand, Australia, Canada, Russia, Wyoming and in other small deposits around the world.

Jadeite is a silicate of sodium and aluminium. Nephrite is a silicate of calcium and magnesium.

Do they look different?
Yes, Jadeite is a rare mineral and the lighter brighter colours have the greatest value. Nephrite is richer in colour with interesting inclusions, rivers and other variations of colour. It can be either dark or light - from almost black-green, through greens, rust to light, - nearly white in colour.

Is one kind of Jade more valuable than the other?
No, the preference is personal. Some people like dark stone and some prefer light coloured stone. The preferences generally depend on where you come from - your ethnicity. There are two schools of thought to be aware of: the Maori school and the Asian school of Jade appreciation. The Maori school prefers their stone to be rich in colour, either dark or light, with interesting inclusions, rivers and other variations. The Asian school has developed over the last 5,000 years and prefers lighter brighter colours with clarity and purity.

Why is Jade called Greenstone in New Zealand?
This name came from the first European explorers who came to New Zealand in the eighteenth century and saw the Maori people wearing Jade tiki and other ornaments. They didn't realise it was Jade and called it Greenstone and the name has stayed.

What should I look out for when buying Jade?

Check for cracks. Hold the piece up to the light and study it carefully. If there are any cracks they will be a point of weakness and could cause your piece to break later on.
Look for richness of colour. Some Jade can be muddy or dull in colour.
Look for translucence. The beauty of Jade is seen in the way light reflects and moves through the stone.