 The most desired gems have always been sapphires and rubies. They both belong to the corundum group characterized by its hardness (9 on the Mohs scale) which is only exceeded by that of diamond.
Sapphire is mainly known in all blue shades however it also comes in all other colours of the spectra except for red.
RUBY on the other hand can only be red of many shades depending on its origin. There is a continuous range from pink sapphires to red rubies. Ruby is extremely rare and usually smaller than sapphire which causes its higher price.
 Emerald is also a very popular gemstone. It belongs to a large family of the beryls and is characterized by its green colour. Compare to other beryls emeralds can hardly be seen without inclusions. Other members of this family are aquamarine (different shades of blue often with greenish shimmer), morganit (pink tones) and heliodor (greenish yellow) all of hardness 7,5-8 on the Mohs scale.
 TOPAZ is fancied too. Its hardness is 8 and is most commonly found in yellow but comes also in blue, red, green and sometimes it is colourless. In its coulourless form it is used as diamond substitute.
Very attractive and appreciated form of the gemstone zoisite is its blue variety tanzanite (hardness 6-6,5). No less interesting are garnets in many shades of red known as pyrope (Bohemian garnets, rhodolites, almandines). Among green garnets varieties the most popular are tsavoite and rare demantoid. Grossularite comes in yellow and hessonite in orange. Peridot is a very old gemstone which has always been appreciated for its radiant olive green colour (hardness 6,5-7).
 Out of the group of quartz (hardness 7) violet amethyste, yellow citrine, smoky morion and colourless crystal are haunting and often used in jewellery.
Mohs scale of mineral hardness
1.Talc, 2. Gypsum, 3. Calcite, 4. Fluorite,
5. Apatite, 6. Orthoclase Feldspar, 7. Quartz,
8. Topaz, 9. Corundum, 10. Diamond |
