A shape of pearl. The shape is not round but is symetrical, having similar characteristics on opposite sides

A flaw (blister or spot) on the surface of a gem

A hard mineral that exists in the form of coloured crystals, such as rubies and sapphires

The weight of a material as compared to an equal volume of water

The coloured light reflected from within a diamond through the crown. It is maximized by cutting a diamond to the correct proportions

The narrow band around the widest part of a faceted stone

What is measured with the Moh's scale?

A term used to describe the attributes of a gemstone's colour

The hardness of Feldspar is...

The iridescent lining of an oyster shell

The shape of a stone rounded at one end and tapered at the other

The ratio of the velocity of light in air to its velocity in the new substance

A classification scale ranging from light to dark, which indicates colour density

What is a table on a stone?

On the Moh's scale what number corresponds to:

'scratched with a knife with difficulty'

What stone can be 'can be scratched by the fingernail'

What nationality was the person who devised the Moh's scale

the progression 9 to 10 on the Mohs scale reflects a hardness increase of more than ...................... percent.