Sunday, November 14, 2010

Chatoyant Pietersite

Pietersite is the name given to a beautiful mineral aggregate that is most often cut into cabochon shapes and makes a great gemstone material. It is closely related to tiger eye and is prized for its chaotic bands and swirls of dark red, gold, brown and sometimes blue. Areas of the stone often display a characteristic known as “chatoyancy”. Chatoyancy is a shimmering, cat's eye effect caused by tiny, fibrous, parallel inclusions.

It is named for Sid Pieters who first discovered it in Namibia in 1962. A slightly different material was later discovered in China and was also classified as Pietesite. I have read that the China mine is closed and so there is no new material coming out of China or Namibia. In any event, supplies are very limited.

Pietersite that contains a lot of blue is the rarest. Dark red is more common. The rich, earthy colors, chatoyant characteristics and striking patterns make it a popular stone year round, but especially in the fall.

Friday, October 08, 2010

Crazy Cool Idocrase

Idocrase is a very interesting mineral. It also can be a very beautiful gemstone! Idocrase also goes by the name Vesuvianite, since it was first discovered on the volcano, Mount Vesuvius! It isn't very well known outside of rockhound and gem collectors circles but as more high grade material is becoming available, especially from East Africa, it is gaining a wider following. Idocrase is usually an opaque dark green. The opaque material has sometimes been used as a simulant or substitute for jade.

The really exciting stuff though, is the bright, translucent pieces! Somewhat included specimens can be cut into beautiful cabochons and cleaner pieces are facet cut. The shade of green varies from slightly yellowish-green to strongly yellowish-green. The color is reminiscent of the popular gemstone peridot.

If you are looking for a green gemstone that is a little out of the ordinary, consider idocrase. It goes well with amethyst and looks great set in silver.

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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.

Thursday, August 05, 2010

The New Opal from Welo Ethiopia

There is a lot of excitement about a new opal find in the Welo (sometimes spelled Wello) region of Ethiopia. It was discovered in 2008 and is considered the most stable opal found in that country. Opal from other areas of Ethiopia is often very beautiful but has a reputation for being unstable (prone to cracking or crazing). This Welo opal takes a little patience to cut properly, but once cut has proven to be every bit as stable as Australian opal. The fire is generally very bright, usually 4 to 5 on the 5 point brightness scale! They display the full spectrum of colors with red being very prevalent. They also display a wide range of fire patterns and base colors. If you look closely at the opal pictured, it shows an unique feature sometimes seen in Welo opals. It shows an internal cellular pattern sometimes called honeycomb. This structure is apart from the base color or the fire pattern. You'll also notice that it has a bi-colored base, being amber colored on the right side and translucent milky white on the other side.

The opal material from Welo is usually hydrophane, which basically means that it can absorb a lot of water. When dry hydrophane is soaked in water, it causes the base color to clear up...sometimes highlighting the play-of-color, sometimes making it vanish! If soaked in water, it can take from a few hours to two weeks to completely dry out and return to it original state. Do not try and accelerate the drying by any artificial means like a lamp, for it could cause cracking. The price of this opal has risen dramatically and well may continue to do so. The Ethiopian government has taken control of the mines and is controlling most all of the material coming onto the market now. On the right is a picture of a piece of Welo opal rough.

Anyone who loves and appreciates opals is sure to fall in love with Welo opals. They can be mesmerizing! The colors can be almost unbelievably bright. They show an endless variety of base colors, patterns and colors.

Friday, March 26, 2010

Dendrites, Beautiful Gemstone Inclusions

You may have heard the term dendrite or more likely the adjective, dendritic, used when describing a gemstone and wondered exactly what it was. They are attractive patterns, usually black or dark brown that are seen in many types of gemstone material. They are most often associated with agates but are sometimes found in quartz, opal and other stones. They are also commonly seen in limestone.

The word dendrite comes from the greek word for "tree" because a dendritic inclusion in a stone looks like a branching tree or at least like some type of plant life. They are often said to look like ferns or moss and many people mistakingly speculate that they are fossil imprints of moss. Actually dendrites are inclusions of manganese crystals. They are formed when manganese rich water seeps into tiny crevices in rocks and the manganese crystals are deposited in intricate branching patterns. The result, if properly cut, is a facinating gemstone.
As I said, the most common dendritic gemstone in dendritic agate, the most famous probably being from Russia or Kazakhstan. They are generally white with black or brown dendrites. The famous Russian jeweler Carl Faberge used them and made them popular in the late 1800's. I've also seen some blue Peruvian opals with dendrites that were strikingly beautiful and clear quartz with dendrites are not uncommon.
Dendrites in Opalite
Visit my website: to see more dendritic gemstones.

Thursday, January 28, 2010

What is Drusy?

Drusy, often spelled "Druzy" is a layer or crust of tiny crystals on the surface of a rock. Most often it is found in a crevice or on the inside surface of a geode. I suppose it could be any kind of crystal, but usually it is referring to quartz crystal.
Drusy has become very popular in recent years as a cut, jewelry stone. A section of the drusy bearing host rock is cut out and shaped, usually with a flat back, similar to the way a cabochon is made. The drusy crystals on top are left intact. In the example on the left, the host rock around the edges has been polished. Sometimes the Drusy goes right up to the edges.

The drusy is sometimes clear quartz and sometimes amethyst or citine. Most often though, the crystals have been treated in some way to change or enhance the color. The majority of druzy is naturally a dull grey color. One common technique coats the crystal with another metallic element such as titanium or cobalt to give the drusy a really sensational look! The picture below is a titanium coated druzy.
This permanent treatment is done in a vacuum chamber and can be very difficult to do properly. Other times the material is dyed or is otherwise diffused with color.
The finished stones can be set in jewelry with a bezel or prongs. They also make great wire wrapping subjects. Drusy gemstones make great jewelry stones . They are usually quite durable and definitely are real attention grabbers.

Tuesday, January 05, 2010

Fossil Coral

One of my favorite gemstone materials is fossil coral. The flower-like patterns in the stone are amazingly intricate and beautiful. It is the fossilized remains of prehistoric corals. Most that I've seen comes from the mountains of Indonesia. As there are many different species of coral, there are different patterns of fossil coral available. There are also different colors. A light tan seems to be the most common but there is also dark brown, reddish brown, black and gray as well as some that is multi-color or banded. Most is opaque, but I've seen some translucent specimens.

Generally, stones with crisp, clear detail are more expensive. More unusual or attractive coloring also influences value. It is availabe as cabochons or beads.