The Phoenix Chapter hosted the annual ARCS Holiday Luncheon and General Board Meeting on December 15th at Elements at the Sanctuary Resort in Paradise Valley. The featured guest speakers were gemologists Ginnie Schmitt and her son Michael, from Schmitt Jewelers, offering an interesting presentation “Gemology-the Geoscience”.
Michael explained through his power point presentation that diamonds consist of pure carbon made deep in the earth’s crust where conditions of heat and deep pressure are perfect for diamond formation. This stone is ranked the hardest of all gems on the Mohs scale. The Mohs scale of mineral hardness is a qualitative ordinal scale that characterizes the scratch resistance of various minerals through the ability of a harder material to scratch softer material. Found throughout the world, diamond deposits are mostly mined in two specific ways, through open pit mining and alluvial mining. As Kimberlite rock containing diamonds erodes over time by rivers and streams, the sediment can carry diamond deposits downstream. The process of alluvial mining involves digging and sifting through mud, sand and gravel, with shovels and sieves and bare hands in these drainage areas, and is mostly done by small-scale miners.
Color, Clarity, Carat and Cut are the 4 C’s of diamond classification. The 4 C’s provide a way to objectively compare and evaluate the diamonds features and worth. One carat is equal to 200 milligrams in weight. The GIA Clarity Scale includes eleven clarity grades ranging from Flawless to Included and describes the amount of natural characteristics within the stone. The diamonds relationship with light is reflected in its cut. The GIA Cut Scale denotes the brightness, fire and scintillation that the diamond projects as it interacts with light, a combination of the diamond’s fine proportions, symmetry and polish. Truly colorless diamonds are extremely rare. Color is graded in the GIA Color Scale from D (colorless) through Z (light yellow or brown) and is mainly caused by trace elements such as chromium and iron and titanium in the stone, and also through other chemical compositions in the stone. The letter of the scale represents a range of color and is a measure of how noticeable the color is. Inclusions of a diamond can make for a beautiful stone that changes color as the light changes.
Various tests are used by the jeweler to determine the type of stone and to decipher a natural versus synthetic stone. Tests include the Refraction Index, specific gravity, spectrum and magnification, among others.
Thanks to Terry Applefield and Sydney Fox for arranging this wonderful holiday event for our Phoenix Chapter.