Tuesday, September 14, 2010

Colorful Gem Chalcedony

Chalcedony is a fairly common stone that has been used for centuries for tools and adornment. It is a form of quartz, called micro-crystaline simply meaning that it is very fine grained. Since it is very hard, it was a popular choice among prehistoric types for making ax heads and weapons. Today it is used primarily as a gemstone.

Although it is a very common stone, you may be unfamiliar with the name chalcedony. By the way, if you've read the word but never heard it pronounced, you might be surprised to learn that it is pronounced cal-SID-nee. The reason you may not have heard much about it before is that different colors of chalcedony are given different,more glamorous sounding names. For instance, I'm sure you've heard of Carnelian. Carnelian is red chalcedony. Onyx is black chalcedony. Green chalcedony is called chrysoprase or chrysophase. Banded chalcedonies are usually called agates. Recently though, some of the other, more exotic colors are getting more attention and used as gemstones. And they are just being called chalcedony. Blue chalcedony has been popular for a while now. And Indonesia yields some gorgeous purple chalcedony that is the color of amethyst as well as some beautiful bright yellow specimens. Nice clean, clear pieces of this purple or yellow material sell for $20 per carat or more.
A lot of chalcedony is dyed or otherwise treated to enhance its color. Most of the carnelian on the market is heat treated or dyed and almost all onyx dyed to make it blacker.. There is also some very pretty, turquoise blue chalcedony being sold that are recieving a diffusion treatment. The important thing is to always ask before you buy. Gemstone treatments are ok as long as they are disclosed. Natural, untreated chalcedony is much more valuable than dyed stones and the color is permanant. The color of treated stones sometimes fades over time. I have seen beautiful blue chalcedony turn grey after being exposed to light for a few months.
Chalcedony is in many ways a perfect gemstone. The colors are bold, striking and wide ranging. Nice specimens have just the right amount of translucency, so they almost look like they are glowing from within. And they are extremely durable! Best of all chalcedony gemstones, for the most part are affordable.

Wednesday, September 01, 2010

Turquoise: Natural or Not?

One of the most popular gemstones in America has long been turquoise. Usually associated with the desert southwest and the Native Americans of that region, it seems that turquoise jewelry is always in style. It comes in a wide variety of colors and quality and a wide range of prices. If you are in the market to buy turquoise, it is critical that you know exactly what you are getting.

There are legally five different forms of turquoise.

  • Natural Turquoise - This turquoise is not treated in any way. It is naturally hard enough and beautiful enough that it is just mined, cut and polished. By some estimates, less than 3% of all turquoise on the market is natural! This is the most valuable and collectible form of turquoise.

  • Stabilized Turquoise - This turquoise is naturally beautiful, but was a little too soft to be practical as a jewelry stone. It has therefore undergone a process to harden it. It is usually infused, under pressure, with a clear epoxy resin. The resin allows the turquoise to be cut and polished and makes it much more durable. Another process has more recently been developed that involves vaporized silica being infused in the turquoise. Most of the turquoise on the market is stabilized in some way. It should be less expensive than completely natural material. Although less valuable, it is real turquoise and makes beautiful, affordable jewelry.

  • Treated Turquoise - It is soft turquoise that has been stabilized as described above, but The color has also been enhanced. Normally a dye is added to the epoxy in order to improve the color of very light or poorly colored material. The colors usually look a little artificial. It should cost much less than natural or stabilized turquoise.

  • Reconstituted Turquoise -Very low grade turquoise "chalk" that is ground into powder, saturated with epoxy resin, dyed, and compressed into blocks. The blocks are then cut and shaped into stones to be put into jewelry. Obviously, these stones should be very inexpensive.

  • Imitation Turquoise - These contain no real turquoise at all. They may be an entirely artificial material like a plastic or they may be some other type of stone that has been dyed to look like turquoise. Howlite, which is a very common, naturally white stone, is often used since it is a similar looking texture and is porous and takes dye easily.
Techniques for treating and imitating turquoise are constantly improving and it is becoming very difficult to tell sometimes whether or not a stone is treated or even if it is real. Experience will help you spot fake or treated stones. Once you've looked at a lot of genuine turquoise you will develop a sense of what looks real and what doesn't. Genuine turquoise has a somewhat waxy look, not too glossy. If nuggets are darker in high areas and lighter color in the low spots they are probably dyed. If buying beads, look in the hole! If it is white inside, it is fake. But even experts can sometimes be fooled. Your best bet is to buy from a reputable dealer. They should disclose if it is natural, treated or imitation and offer a money back guarantee.