All precious and semi-precious stones used in jewellery are graded for hardness using the "Mohs Scale" which was developed in the early 19th century by mineralogist Friedrich Mohs. The scale ranges from the hardest mineral which is diamond - rated 10 - down to amber, ivory and tortoiseshell - rated 2 - and can be used as a general guide as to how robust a stone will be when exposed to everyday wear. Consider that ordinary dust contains minute grains of quartz, which is rated at 7. All stones, regardless of their place on the scale are brittle and can be fractured by a hard blow.

It should also be borne in mind that some stones, such as turquoise are porous and can be damaged by immersion in water and that detergents can dull the colour and natural lustre of many stones, particularly emeralds.

By taking sensible precautions, your jewellery should give you many years of wearing pleasure.