 Gemstones or gems come in a variety of precious and semi-precious stones; including sapphires, rubies, quartz and amerthyst etc.. Gemstones can be pieces of attractive and beautiful stones when cut and polished.
Gemstones are used to make jewellery and other adornments. Most gemstones or gems are hard, but some soft stones and minerals are also used for jewellery because of their great lustre. Stones which are transparent are normally faceted, this shows off the stone's interior by reflecting light which the viewer sees as sparkle. Stones which are more opaque such as opal, turquoise, quartz etc.. are cut as cabochons.
Hardness Scale
Is for measuring the gemstones and minerals resistance against abrasions and stcratching. The hardness scale or Moh's scale is named after the German mineralogist Friedrich Mohs. In c1822 he created the scale to measure the hardness between various minerals. It was based on ten minerals which was readily available at the time.
The scale grades the minerals and gemstones from a "10" which is very hard, to a "1" which is very soft.
Below lists some of the minerals and gemstones with their hardness rating...
Diamond 10.0
Corundum 9.0
Sapphire 9.0
Star Sapphire 9.0
Ruby 9.0
Chrysoberl 8.5
Spinel 8.0
Topaz 8.0
Aquamarine 7.5 - 8.0
Beryl 7.5 - 8.0
Emerald 7.5 - 8.0
Garnet 7.0 - 7.5
Iolite 7.0 - 7.5
Amethyst 7.0
Ametrine 7.0
Quartz 7.0
Tourmaline 7.0 - 7.5
Pyrope Garnet 6.5 - 7.5
Spessartite Garnet 6.5 - 7.5
Zircon 6.5 - 7.5
Chalcedony 6.5 - 7.0
Jadeite 6.5 - 7.0
Jasper 6.5 - 7.0
Peridot 6.5 - 7.0
Moonstone 6.0 - 6.5
Opal 5.5 - 6.5
Lapis 5.0 - 6.0
Turquoise 5.0 - 6.0
Cat's Eye Apatite 5.0
Fluorite 4.0
Gypsum 2.0
Talc 1.0
 Carats
A carat is the measurement of weight for gemstones. Chart below shows carat sizes and width in millimeters, Images are approximate only.
Carat Size Stone size Width in Millimeters
0.03 carat  2.0mm
0.05 carat  2.5mm
0.07 carat  2.7mm
0.10 carat  3.0mm
0.15 carat  3.4mm
0.20 carat  3.8mm
0.40 carat  4.8mm
0.50 carat  5.2mm
0.65 carat  5.6mm
0.85 carat  6.2mm
1.00 carat  6.5mm
2.00 carat  8.2mm
5.00 carat  11.00mm
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