information about on materials used in jewellery
information about on materials used in jewellery
gold silver and platinum are valuable used in jewellery .
gold is especially important , because it is easy to work and it does not tarnish, as silver does .
the leading gemstones are diamonds , especially ,colourless ones, and three coloured gems rubies and sapphires (varieties of the mineral corundum )and emeralds (varities of beryl ).
probably the most valuabble of these gems is now the ruby .
these four gemstones have several features in common .
they are all hard and hence ,long -wearing .
their hardness ranges from diamond the hardest of all natural substances to ruby and sapphire which rate 9 on the Mohs, scale and emerald which has a hardness of 8
the annual world production of diamonds in the mid- 1970 was about 46 million carats (about 9200 kg ,) but less than one- fourth of diamonds prodcced are suitable for jewellery .
many other minerals are used in jewellery .
they are include transparent varieties of granets peridot various types of quartz sphene , spinel, spodumene, topaz , tourmaline ,,turquoise and zircon .
jewellers also ues translucent but beautfully - coloured minerals
including agate , chalcedony and jadeite
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