Wednesday, September 23, 2009

Gemstone Treatments

The topic of gemstone treatments can be confusing for someone shopping for a gemstone. Many people are surprised to learn that most finished gems being sold today have been treated in some way. But that it isn't necessarily a bad thing. The most common treatments are heating, irradiating, dyeing and diffusion. Many types of treatments are considered acceptable in the jewelry trade while others are not. The important thing is that the treatments are disclosed so that you can make an informed buying decision.

The purpose of a treatment is generally to make a gem more beautiful than it would be without the treatment. Some treatments may make a stone more durable. In most cases the treatment is acceptable if it is permanent, improves the qualities of the gem, is disclosed and is not meant to mislead the buyer.

A few types of gems including garnet, peridot and iolite are not usually treated, but most other familiar gemstones usually are. For instance, most all sapphires are heat treated to improve their color and clarity. Heated sapphires display brighter, more even color that would be extremely rare in a natural stone. Therefore most commercially available sapphires have been heated. That usually means you can a afford a more beautiful stone than you could if sapphires were not heated. Heat treatment is widely accepted in the trade. Most of the amethyst now being sold has also been heat treated to improve the color and make it more even.

Some sapphires receive diffusion treatment to alter their color. Through heat and pressure, a particular chemical element is diffused into the cut stone, thereby changing the color. That' the case with many- of the “padparadscha” (pinkish-orange) sapphire that is on the market. However diffusion only effects a thin outer layer of the stone, so if the stone is scratched a little or chipped the original color will show. For that reason, this is often considered an “unacceptable” treatment unless the buyer is fully aware of the treatment and its risks.

Many people like the idea of having an untreated stone. They feel that part of the attraction of gems is that it is something created by nature, without any human manipulation. They prefer untreated stones even if it is more expensive or they have to sacrifice color or clarity a little. Treatment is so commonplace that untreated gemstones are becoming rare and so, they may have more value to a collector or purest.

Below is a list of some of the treatments that are usually deemed “acceptable” by the jewelry trade:

  • heating sapphires and rubies
  • heating aquamarine, amethyst, citrine, tanzanite, topaz, tourmaline, and zircon
  • irradiating topaz (to make clear topaz blue)
  • putting organic resins and wax in emeralds
  • waxing lapis lazuli, jade, and other opaque gemstones
  • dying onyx black

Many of these treatments are virtually undetectable, so whether or not they are treated is difficult to prove. Many stones are sold as “probably treated” and you should assume the stones you are buying are, unless it is specified as “untreated”. You may see the term “natural used”. The term “natural gem” means that the stone was formed in the earth. In other words, it is not synthetic, man-made or lab created. But it may be treated and can still be called natural!

Here are some of the treatments that are usually considered “not acceptable”:

  • diffusion treatment of sapphire
  • glass filling of ruby
  • epoxy resin in emerald
  • dyeing lapis lazuli blue, or most other dye treatments
  • epoxy treatment of jadeite

Even these treatments are not illegal or even unethical as long as they are fully disclosed. Ultimately, it is a personal decision whether you buy a treated, untreated or synthetic gemstone. The important thing is that you know what you are buying.

Saturday, September 19, 2009

Iolite: Beautiful & Affordable Blue Gem

Do you love blue sapphires or tanzanite but they don't quite fit your budget? Consider iolite! This gemstone is probably not as well known or as often used as it deserves. It is the gem variety of the mineral cordierite.

Iolite Has very pronounced "pleochroism". That means that the color looks different when you look at it from different angles. Because of this property, the Vikings were able to use thin pieces of iolite to navigate, using it to determine the exact location of the sun even in bad conditions. The same stone can look violet- blue or yellowish-gray or even clear depending on how it is viewed. For that reason, it is very important that the stone be properly cut so that when it is viewed face up, you see the best color. Sometimes it is called "water sapphire", although the best colored specimens actually look more like fine tanzanite.

It is mined in Brazil, Sri Lanka and several locations in Africa. It's relative hardness and beautiful color make it a great jewelry stone. And the price is surprisingly affordable. A very nice stone can be had for under $10 per carat. If you dream of some day owning a large tanzanite, but you are still a few thousand dollars short, a nice iolite will make a good place holder in that ring setting for now.
You can see some more iolites here and some iolite earrings here.

Wednesday, September 09, 2009

Rutilated Garnet

You may be familiar with the gemstone rutilated quartz. It is a fairly common stone that can be strikingly beautiful. It is clear quartz that has inclusions of rutile crystals within it. The rutile appears as long, thin, needle-like crystals that are black, gold or often reddish-brown in color. I have occasionally found a rutile inclusion here or there in other types of gems, but usually its just a couple of thin lines in the gemstone and is a detractor from the stones appeal rather than something that enhances its beauty and value. Recently though, I got some faceted grossular garnets from Africa. A couple of them were quite heavily included with rutile. Here's a picture of one. The garnet is a pale green color with a number of gold rutile crystals running through it at various angles. Its very interesting and I think, attractive! Garnets

Tuesday, September 08, 2009

Color Change Garnets from Kenya

I wrote back in January about color change garnets. Now I actually have some in my hand, so I'd like to revisit the subject. Garnet is one of only few gemstones that can exhibit a color change. A color change gem is one that appears to change from one color to another color depending on the light source. The atomic structure of the gemstone reacts differently under the ultraviolet rays in natural sunlight (or fluorescent light) .

I have two different types of material. I have some that are larger stones in the 2 to 3.5ct. range. They have beautiful brilliance and scintillation. The color change isn't 100%. In outdoor light they are a slightly pinkish-brown color but with bright red highlights. In indoor light they are more of a raspberry pink color that reminds me of some pink tourmalines that I've seen. They are really gorgeous stones!

The other ones that I have are the really rare ones that were just discovered in Kenya in the last year. They show a very strong color change from kind of a steel blue in daylight to purple in incandescent lighting. I have 2 of these, both under a carat. These are real collector's items
Follow the link to get more details on some of these color change garnets.

Friday, September 04, 2009

East African Rubies

The world's best rubies have traditionally come from Asia, most notably Burma and Thailand. Africa has long been a source of rubies, but mostly brownish or purplish stones. Most were opaque or heavily included. In recent years however, there have been several finds of ruby deposits in east Africa that are a beautiful red or pinkish-red color. Although most are best suited to cabochon cutting, some have facet grade clarity. The biggest producing countries in the are Madagascar, Tanzania and Kenya. I recently obtained some beautiful cabochons that were mined near the Tanzania-Kenya border. Most have some, spots, fissures or other inclusions but the color is fabulous and the prices are great. They are ideal for jewelry artists who would like to add some precious gems to their collection without spending hundreds of dollars on a stone. They are of course very durable and easy to work with. They can even be set and baked in Precious Metal Clay. You can have a look at some of these ruby gemstones here. They are priced from $8 to $100 depending on the size and quality.