Note #2 from Jill
I have taken my first class offered by the GIA (Gemological Institute of America), “Colored Stone Essentials.” I discovered a few interesting items I thought you would enjoy.
There are two types of stones, Organic, and Inorganic. Organic stones are formed by biological processes which include the remains of saltwater sea creatures, tusk bearing animals, and from plant life. Inorganic stones are natural minerals with specific chemical and structured composition. The shape of a stone is determined by its atomic structure. A stone’s identity is determined by its chemical composition, (kinds and quantities of a gem’s atoms) and its crystalline structure (the arrangement of atoms). Both characteristics determine how gems are classified into species, Beryl, Corundum, and Quartz, etc. If the stone varies in chemical or crystal structure, but have one of the two in common they are classified into groups; Tourmaline, Spinel, Garnet, or the most common of the Earth’s minerals, Feldspar which is found in Moonstone and Porcelain. The inclusion of trace elements, impurities, creates defects replacing some atoms. Defects mainly affect the color of the stone and potentially its value if it detracts from the visual appeal.
Any stone other than a Diamond is considered a Colored Gem. Colored Gems must share three important traits, beauty, rarity, and durability.
Beauty: Finished gems appeal comes from combining the elements of color, symmetry, and surface appearance. Color is the most important consideration when buying gemstones. Symmetry, the cut, should be balanced and harmonious. Surface appearance, or luster, for most gems, requires them to be highly polished.
Rarity: Although most people believe rarity increases value, it is not always the case. An example is Pink Spinel which is durable and rare but has little demand. Rarity is important, but a gem must be popular as well. Tanzanite, a violet blue gem is a good example. Known as a generational stone, Tanzanite was discovered in East Africa in 1968. In the last few years, those mines have been depleted of quality stones.
Durability: Hardness, toughness, and stability determine Durability. Hardness and toughness are not the same. Hardness speaks to the gems resistance to scratching and abrasion. Toughness speaks to resistance to cracking. Stability is the resistance to heat, light, and chemicals, especially jewelry cleaners.
A jeweler friend tells a story how he accidentally learned about the composition of Turquoise and its stability. Early in his career he left two stones in the cleaner too long which disintegrated the Turquoise stones. In the debris was copper. So he learned that copper is a component of Turquoise and that too much time in the cleaning solution is problematic. It was a difficult lesson to learn but it may be something to remember the next time you hand your jewelry over to someone who offers to clean them. Every jewel has various levels of stability and can easily be ruined by a variety of chemicals.
I would be so happy to hear from you. Let me know what’s on your mind!