Emerald

Emerald is another form of the mineral Beryl - with trace amounts of Chromium ensuring that it is a green hue.

Emeralds range in colour from Yellow-green to Blue Green and have a hardness of 7.5 to 8 on the Mohs scale and are normally found in a raw state as a hexagonal crystal normally with large amounts of "inclusions" (foreign matter) which means their resistance to breakage is classified generally as poor.

Due to the fact that most emeralds have small surface reaching cracks, they are oiled as part of the "post-lapidary" process in order to fill these cracks and improve their clarity and stability - generally with Cedar Oil which has a similar refractive index and oil-treated emeralds although sometimes looking better, are far less valuable than an untreated stone.

Here you can see examples of Emeralds in various forms.