Precious and Semi- Precious Stones
Precious and semi-precious stones also called gem or jewel are a group of minerals which because of some properties, these substances are distinguished from other minerals and stones. Most of gems are made of mineral crystalline substances.
Recognition and use of live and beautiful stones or gems enjoy a longtime antiquity over 7000 years. Agate, quartz, amber, garnet, jadeite, emerald and turquoise can be named among the first known gemstones. Value and preciousness of gems is due to some of their features like color, firmness, beauty and brightness. Apart from these features, they are valuable because of their rarity. In addition to being valuable, precious stones have magic aspects too. Also it was believed that some stones are effective as curative of diseases and physical troubles. The oldest method for decorating them and representing their beauty has been engraving shapes and letters on them. It is supposed that for the first time jewel crystals were cut in India.
By the early 15th century, cutting and polishing the valuable gems was limited to burnishing the natural plates which ought to be pellucid like agate which is only cut and to be appeared more attractive is polished by emery paper. It is believed that cutting gemstones was initiated in the 15th century and it was also completed and prevailed to some extent. In Iran, this profession has been under the title of gem cutting or engraving which has been applied for cutting semi-precious stones. In the past, there were many demands for turquoise, agate, garnet and many valuable stones in Iran and they have been used as jewelry or as amulet to give protection against evil eye or danger. The tool for gem cutting was engraving wheel having one rotation axis that rotated with a rim. Nowadays with development in industries and quality of the products, equipped cutting machines are used. Gem cutting in Iran has chosen a new route using modern style and exists in two main forms:
1- cutting polyhedral precious stones and
2- engraving which includes making small statuses and engraving on stones.
