| GEM |
HARDNESS |
GENERAL SPECIFICATIONS - INFORMATION |
| Diamond |
10 |
Diamond has a wide bandgap of 5.5eV corresponding to the deep ultraviolet wavelength of 225 nanometers. This means that pure diamond should transmit visible light and appear as a clear colourless crystal. Colours in diamonds originate from lattice defects and impurities. |
| Ruby |
9 |
All natural rubies have imperfections in them, including colour impurities and inclusions of rutile needles known as "silk”. |
| Sapphire |
9 |
The sapphire is one of the two or three gem-varieties of corundum, with another one being the red or deep pink ruby. Although blue is their most well-known colour, sapphires are made up of any colour of corundum except for red (red ones are called rubies). Sapphires may also be colourless, and they are also found in shades of gray and black. |
| Imperial Topaz |
8 |
Imperial topaz is yellow, pink (rare, if natural) or pink-orange. Brazilian Imperial Topaz can often have a bright yellow to deep golden brown hue, sometimes even violet. Many brown or pale topazes are treated to make them bright yellow, gold, pink or violet coloured. Some imperial topaz stones can fade on exposure to sunlight for an extended period of time |
| Topaz |
8 |
Pure topaz is colourless and transparent but is usually tinted by impurities; typical topaz is wine, yellow, pale gray, reddish-orange, or blue brown. It can also be made white, pale green, blue, gold, pink (rare), reddish-yellow or opaque to transparent/translucent |
| Beryl |
7.5 / 8 |
Pure beryl is colourless, but it is frequently tinted by impurities; possible colours are green, blue, yellow, red, and white. |
| Emerald |
7.5 / 8 |
Emerald refers to green beryl, coloured by trace amounts of chromium and sometimes vanadium |
| Kunzite |
7 |
Kunzite is a pink to lilac coloured gemstone, a variety of spodumene with the colour coming from minor to trace amounts of manganese. Some (but not all) kunzite used for gemstones has been heated to enhance its colour. It is also frequently irradiated to enhance the colour. Many kunzites fade when exposed to sunlight. |
| Amethyst |
7 |
Amethyst is the violet variety of quartz. The colour in amethyst is due to irradiation, which caused the iron ions present as impurities in quartz to rearrange themselves in the crystal lattice affecting the colour in a reversible process. |
| Citrine |
7 |
Citrine is a variety of quartz whose colour ranges from a pale yellow to brown. Natural citrines are rare; most commercial citrines are heat-treated amethysts or smoky quartzes. It is nearly impossible to tell cut citrine from yellow topaz visibly, but they differ in hardness. Citrine has ferric impurities, and is rarely found naturally. |
| Axinite |
6.5 / 7 |
Axinite is a brown to violet-brown, or reddish-brown gem-stone. |
| Garnet |
6.5 / 7 .5 |
Garnets are found in many colours including red, orange, yellow, green, blue, purple, brown, black, pink and colourless. The rarest of these is the blue garnet. It changes colour from blue-green in the daylight to purple in incandescent light, as a result of the relatively high amounts of vanadium. Other varieties of colour-changing garnets exist. In daylight, their colour ranges from shades of green, beige, brown, gray, and blue, but in incandescent light, they appear a reddish or purplish/pink colour. |
| Peridot |
6.5 / 7 |
Peridot is one of the few gemstones that occur in only one colour > olive green. The intensity and tint of the green, however, depends on how much iron is contained in the crystal structure, so the colour of individual peridot gems can vary from yellow- to olive- to brownish-green. The most valued colour is a dark olive-green. It is sometimes mistaken for emeralds and other green gems |
| Kyanite |
6.0 / 7 |
Colours are blue, green, white, grey and black. Use of this gemstone is limited by its anisotropism and perfect cleavage |
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