Green Is Up for August
Green is the color for August gemstones. Peridot, the modern August birthstone includes several shades of green depending on the amounts of iron and trace elements nickel and chromium. The best colors seem to be for amouints of iron below 15%. Peridot is the name given to gem quality material of both fosterite (Mg2SiO4) and fayalite (Fe2SiO4) which together are called Olivine which is written chemically as (Mg, Fe)2SiO4.
One very interesting occurance of this mineral is that it is also found in nickel-iron meteorites called pallasites. These are also occasionally facetted and used in jewelry.
At least 80% of the peridot on the market today comes from Arizona, but the best quality material comes from Egypt, Pakistan and Myanmar. An island in the Red Sea off of Egypt, Zebirget, is also an ancient and perhaps oldest known source of this gemstone. Several other countries around the world also produce peridot but in fal smaller quantities.
Purple Jade Earrings with Bead Netting
Another, less often used, gemstone for August is jade, a milky green amorphous gemstone known for being ameneable to being carved and shaped. There are two different materials allowed to be called jade. Jadeite, Na(Al, Fe)Si2O6, and nephrite, Ca2(Mg, Fe)5Si8O22(OH)2, which is a variety of actinolite. Jadeite, used more in ancient America than in China, occurs in other colors besides green, including greyish green, white, pale shades of blue or purple, and even sometimes yellow or pink. Nephrite is actually the more abundant material but it occurs in only a gradation of a creamy white to green color.
The actinolite family also includes the interesting mineral, asbestos!
A more traditional, if less used nowadays, mineral associated with August is a stone called sardonyx. It is not itself a mineral but rather the name given to a type of agate or onyx, (both of these being types of chalcedony which is a quartz mineral as is jasper and many other minerals and gems). Ancient Greeks, Minoans and Egyptians wore this reddish-brown stone and used it in their art. It was especially popular for use in carving cameos. I have seen the name Carnelian Onyx used for this stone as well.
August 20th, 2009 at 10:27 PM
very interesting.
August 20th, 2009 at 10:57 PM
Thanks, Margaret.