This page was last edited on 8 November 2017, at 15:39. Gem”, “Gems”, and “Jewels” gemstones pdf free download here. Rarity is another characteristic that lends value to a gemstone.
A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. Use of the terms ‘precious’ and ‘semi-precious’ in a commercial context is, arguably, misleading in that it deceptively implies certain stones are intrinsically more valuable than others, which is not necessarily the case. Gemstones may also be classified in terms of their “water”. This is a recognized grading of the gem’s luster, transparency, or “brilliance”.
There is no universally accepted grading system for gemstones. Historically, all gemstones were graded using the naked eye. The GIA system included a major innovation: the introduction of 10x magnification as the standard for grading clarity. With modification, these categories can be useful in understanding the grading of all gemstones. The four criteria carry different weight depending upon whether they are applied to colored gemstones or to colorless diamonds. In diamonds, cut is the primary determinant of value, followed by clarity and color.
In gemstones that have color, including colored diamonds, it is the purity and beauty of that color that is the primary determinant of quality. Today such a distinction is no longer made by the gemstone trade. Many gemstones are used in even the most expensive jewelry, depending on the brand name of the designer, fashion trends, market supply, treatments, etc. Nevertheless, diamonds, rubies, sapphires, and emeralds still have a reputation that exceeds those of other gemstones.
In general per carat prices of larger stones are higher than those of smaller stones, but popularity of certain sizes of stone can affect prices. 50,000 for a collector’s three carat pigeon-blood almost “perfect” ruby. The Diamond High Council, Belgium is one of Europe’s oldest laboratories. Its main stakeholder is the Antwerp World Diamond Centre. 1974 by Guy Margel in Belgium.
Zenhokyo, Japan, active in gemological research. Gemmology Institute of Southern Africa, Africa’s premium gem laboratory. South East Asia, involved in gemological education and gem testing. Henry Hänni, focusing on colored gemstones and the identification of natural pearls. Gübelin Gem Lab, the traditional Swiss lab founded by Eduard Gübelin. Each laboratory has its own methodology to evaluate gemstones.
A stone can be called “pink” by one lab while another lab calls it “padparadscha”. One lab can conclude a stone is untreated, while another lab might conclude that it is heat-treated. Country of origin has sometimes been difficult to determine, due to the constant discovery of new source locations. Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate. A few gemstones are used as gems in the crystal or other form in which they are found. Most however, are cut and polished for usage as jewelry.