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This week's Featured Item!
Our last series on Garnets opened up questions about Moonstone and its’ relatives. Coincidentally, along with Pearls, Moonstone just happens to be a birthstone for June. THE FELDSPAR GROUP. The Feldspar group of minerals (calcium, sodium, or potassium aluminum silicates) is the most abundant building block in the Earth’s crust. It is commonly found in granite, pegmatite, & other igneous rocks. Clay (shale & slate) is formed from decomposed Feldspar. Like the Garnet group, the Feldspar group, also, splits into two distinct sub-groups: The Sodium Potassium “Alkali”
Feldspar – (Sodium/Potassium Aluminum The Sodium Calcium “Plagioclase”
Feldspar – (Sodium/Calcium Aluminum
Between the two sub-groups is Albite – (Sodium Aluminum Silicate). The varieties in each subgroup are caused by the percentage of (Alkali Feldspar) Sodium & Potassium ions, or (Plagioclase Feldspar) Sodium & Calcium ions, within the mineral’s molecules. Also, it is common to have two different varieties of Feldspar intertwined in a single crystal. This intertwining of varieties can produce the visual effects we see in Feldspar gemstones. All Feldspar Gems share the following characteristics:
Listed below, are the major varieties of Gem
Feldspars, along with their specific descriptions and histories. The Sodium Potassium “Alkali” Feldspars – (Sodium/Potassium Aluminum Silicates). Adularia – Moonstone Moonstones are found in a variety of pale shades from beige, green, peach, brown, and white. Uncut, these gemstones can be rather dull, but when cut by a master cutter, who, before cutting, aligns the crystal axis exactly at the zenith of the stone, produces a wonderful cabochon that shows off the Moonstones’ exciting sheen (adularescence). Moonstones’ adularescence is caused by light being refracted and scattered when it hits the microscopic lamellar structures (an intertwining of two different forms of Feldspar) within the crystal. “Cats’ Eye” and multi-rayed “star” Moonstones are found in India. The wonderful “Rainbow” Moonstone, with its’ blue sheen comes from Sri Lanka. Moonstones’ classic discovery point is in the Adula massif in the Swiss Alps. Adula is the origin of “Adularia” and “adularescence”. Other deposits are found in Brazil, Myanmar, Australia, and North America. In the Los Angeles (California) area, I believe that the beach suburb of Redondo Beach was originally called “Moonstone Beach” because (before the beach was artificially covered with sand) there was an abundance of moonstones along the pebble-strewn seashore. This is also true for a few other California beaches. Historically, the gemstone Moonstone has been associated with the Moon and love. Currently, Moonstone is associated with the month of June (the wedding month). It is said that prosperity and good fortune are promised to those born in this month. Throughout the world, Moonstone is the birthstone for June, but here in the USA we also add Pearls and Alexandrite as Junes’ birthstone. Many cultures claim Moonstone to have mystical and magical powers. In India, it is a bringer of sweet and beautiful dreams. To Arabs, it is a symbol of fertility. In the USA, Moonstones are the official state stones for the states of Florida and New York. In general, Moonstone is cut into cabochons, but it
is also cut into cameos, spheres, and beads. A century ago Moonstones
were very popular, in particular, when the famous French Master Goldsmith,
Rene Lalique and his buddies used the gem, extensively, in their jewelry.
Moonstones, in particular the Rainbow Moonstone with its’ blue
flash, are seeing a renaissance of popularity. |
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