Monday, August 25, 2008

Common Opal, Precious Opal, Fire Opal or Potch

In this post we're going to talk about some more opal terminology. In fact we'll back up and talk about opals in the most general terms. What is meant by opal, precious opal and fire opal.

Opal is noncrystalline hydrous silicon dioxide. In other words it has the same chemical composition as quartz, but contains 1-2% water and it is not crystallized. It is composed of alignments of tiny spheres which form a compact, three-dimensional network. It is the play of light off of these tiny spheres that often gives opal its unique internal iridescence which is called "opalescence"!

If that opalescence is present, the opal is considered precious opal or sometimes noble opal. Precious opal is generally the most sought after and expensive opal. It is what most people think of when they speak of opal. I

If the opal doesn't display this internal iridescence, if it is just semi-opaque to translucent it is called common opal or potch opal. Common opal sometimes has a somewhat attractive, porcelain-like appearance and is suitable for beads.

In some cases common opal is very translucent to transparent with a bright red, orange or yellow color. This makes very beautiful gemstones and is called "fire opal". That term can be a little confusing because the "opalescence" in an opal is often referred to as its fire. But fire opal doesn't necessarily have any "fire"! Fire opal comes mainly from Mexico. They can be cut into cabochons or even faceted. In some specimens there will be some internal iridescence, therefore qualifying it as precious opal.

See opals at

Visit my Squidoo Page on Opals

Wednesday, August 13, 2008

What is Meant By Opal Doublet or Triplet

Virtually everyone loves opals, but they are different from every other precious gemstone. Their beauty doesn't come from their clarity or purity of color. It comes from the "play of color" that is created when light refracts and reflects off of their unique internal structure. More on that another time. Because they are different, different terminology is used to describe them. If you are new to opals you will need to learn some new vernacular.

When you start shopping for an opal and trying to compare one to another, you will hear the terms doublet, triplet and solid used a lot. The difference here are important to the beauty, value and durability of the stones.

Solid opal simply means that the stone is all opal. All other things being equal, that is the best and the most valuable. An opal doublet on the other hand is not all opal. A layer of opal is bonded to a layer of dark colored stone, usually ironstone. Then the stone is cut and polished. The benefits of the doublet are that a thinner piece of opal can be used that otherwise would be too thin. The backing stone gives it added depth and strength. Also, the black background makes the colors of the opal stand out more and look brighter, like a much more expensive opal. So you can own an opal that looks better than your budget could otherwise handle.

A triplet has three layers. It has the backing layer, then the opal layer and then a clear layer, usually quartz. Opal is a relatively soft stone. The quartz top is very hard and gives the stone added resistance to scratches and chips.

The picture above is a solid opal. You can see some doublet opals, triplet opals and solid opal here, on my website at

Tuesday, August 05, 2008


Garnets have been one of the world's most popular gemstones for many centuries. Although gem quality garnets can be some of the most beautiful of gemstones, most are relatively affordable. There are some varieties, like tsavorite and spessartite that can be very expensive, but most are modestly priced. They are mined in almost every county on the planet. Though most of us think of garnets as a red gemstone they come in many colors and shades, including orange, green, and pink! Garnets are not actually a single species of gemstone but are a whole family of gems that share certain physical properties including crystal shape and chemical composition. They are generally grouped into six garnet species: almandine, pyrope, spessartine, grossular, andradite and uvarovite.

To complicate matters even more, garnets are never just one species, but are a blend of two or more of these.
They are usually named for the species that is most prevalent. A garnet that is described as "pyrope", for example, may actually be 80% pyrope, 15% almandine and 5% spessartine. Some specific blends have also been given names of their own. For example, a garnet that is about 2/3 pyrope and 1/3 almandine is called a Rhodolite. Other names you may encounter for types of garnets include mandarin (yellow-orange spessartine), demantoid (usually green), malaya ( may be pink or reddish orange) , hessonite (usually cinnamon brown or yellowish) or tsavorite(green).

Learning, identifying and describing the seemingly endless varieties of garnets is challenging, but they also provide a wide range of prices and colors for every taste. Garnets also provide a source of great beauty and endless fascination for gem lovers and mineral collectors alike.