Colored stones have been set into rings, earrings and pendants since people figured out how to form metal. For thousands of years, these bright and pretty minerals have been snatched from the planet’s surface or fished out of riverbeds, ground till they were smooth and secured into jewelry as nature created them. These minerals were scarce and hard to come by; they had real cash value, and in some cases were – and to this day are – given and accepted in trade for the things we need in life, meals, clothing to wear and shelter. Colored gems were so astronomically priced that only royalty and the most well-off families could afford to wear ornaments showcasing these stones.

In our modern society, the average person is much more affluent, and that truly is a remarkable thing. Most of us can afford to wear rings, pendants and earrings featuring brightly colored jewels now, which means the demand for these pretty stones has risen to unprecedented levels. Only one thing has not changed – these gems are still only available in limited supplies. Mining technologies have become more modern. People now use large digging machines and people understand much more about how stones are created, and so finding hidden sources has become easier in many ways. Man has also made the world much smaller; with modern transportation miners can reach far-away places that produce huge clusters of stone, making our supply of these gemstones much greater. Of course, keeping up with this greater need hasn’t been a simple task; still more consumers are looking to buy these stones on a daily basis.

In many of these gem deposits workers find a finite supply of excellent quality rough gem material. This high quality gemstone rough usually commands a high price . Of course right near the top grade gem material there is normally a large amount of lesser grade rough. At one time, the less costly mineral specimens were marketed to rockhounds who had gemstone collections and the remainder was made into beads and other objects. However, these days gem processing companies have methods to enhance this lesser quality raw gemstone material, making it much more attractive and suitable for setting in jewelry.

Gemstone enhancement is quite common now; these techniques have become an accepted occurance in the industry provided the customer is furnished with a disclosure statement. Regrettably, many salespeople are not adequately educated themselves, and many don’t know that they are obligated to tell their customers about these gem treatments.

How can consumers protect themselves? I recommend researching to get some information – as much as as possible about any gemstone you are thinking about buying before you give your money to the merchant. You’ll find a large amount of information available on the internet, in periodicals and books. Just about any of it of it can be read at no cost to you; it simply requires a little searching and some time to become an informed buyer. I’ve made and sold jewelry set with stones for more than 30 years, and have learned a lot about colored gemstones; in this article I’m writing about some things that should help you. I’ll talk about commonly known gem facts in this article, and when appropriate I’ll get into widely used treatments and enhancements to these gemstones.

The most common colored gemstones found in rings, pendants and earrings these days belong to several gemstone families. The quartz group; the garnet family; tourmalines and topaz are found in many of the sterling silver and gold gemstone jewelry pieces you’ll find found in jewelry and department stores as well as websites. You’ll see others that are also very widely used, and I will try to touch on most of those here. The most commonly set and enhanced gems are gemstones in the quartz family.

The silicate minerals are one of the most common minerals on the Earth. Silicon Dioxide is found in many gems and varieties; these are quartz gems. Even the sand you see at the local beach is mostly silicon dioxide. Natural gem varieties of this mineral group include two basic types; gems that grow in large crystals and gems that are constructed of microscopic crystals. Large silicon dioxide gemstone crystals are found in many places; and the gemstones most associated with them are citrine, amethyst, smoky quartz and milky, crystal or clear rock quartz, sometimes referred to as Herkimer Diamonds (which are not diamonds at all). Impurities cause these minerals to have their identifying colors. Amethyst is purple due to the iron atoms in it; gemstone quality amethyst is the most sought after example of the quartz minerals. Citrine is a closely related gemstone that has a pale yellow to a deep gold color. Two colored gemstones that show the colors of both amethyst and citrine are referred to as Ametrine. The different colors of citrine and amethyst are caused by naturally high temperatures under the Earth’s surface. These gems can vary from a dark, intense hue to pale, nearly colorless. Well saturated gold tone natural citrines are a very hard to find stone; most of the citrine used in jewelry has been color enhanced by heating. Heat treatment of quartz gems is well known – and almost routine – step in processing these gemstones; usually only excellent quality amethyst is not heat treated.

In the recent past a new variety of quartz called “green amethyst”, or Prasiolite has appeared on the market. Although rare, natural prasiolite can be found; but it is almost never clear. Almost all of the green “amethyst” in jewelry is actually artificially heat enhanced amethyst. Heating amethyst usually produces a yellow to brown tone; but depending on where it was mined, at times it can become green. The various hues are caused by the presence of iron atoms, which can be slightly different depending on the mining location.

The “quartz” beads named for fruit so common today … strawberry quartz and cherry quartz etc … are actually not stone at all; most are a type of art glass. These beads are composed of silicon dioxide … just like a quartz mineral. But they’re made with melted and fused sand … they don’t have a natural crystal growth pattern. They are simulated stone … glass. Another type of gemstone that isn’t actually stone is goldstone; this “gem” is art glass with metallic copper flakes suspended in it.

Microcrystalline quartz minerals are agates, chalcedony and jasper. These gemstones are closely related; they vary mostly in how they were formed and their composition.

Chalcedony is nearly always one body color with a translucent appearance; the most common types are carnelian, which is a reddish brown hue; chrysoprase, which ranges from a yellowish to green shade; blue mist chalcedony and the popular black onyx. Many carnelian and black onyx gemstones are dyed – to achieve an even color. The most valuable kind of chalcedony is a saturated bottle green color chrysoprase. Bloodstone, or Heliotrope is a kind of chalcedony that’s usually a deep green with dots of red jasper.

Jasper is almost always a single body color with a speckled pattern. Well known jasper types are ocean jasper, which has orbicular patterns; red jasper and picture jasper.

All agate gems display patterns. Most agate is recovered from geodes. Popular types of agate may be black sardonyx, plume agate, Lake Superior agate and petrified wood.

All of these are silicon dioxide minerals. The garnet group of minerals that are also a silicate based gem family that find their way into the jewellery many people love to wear on a daily basis … however, garnet isn’t a member of the quartz group. They have a different crystal growth pattern and chemical composition.

There are six types of naturally occuring garnet, and each has several varieties. More often than not, you’ll come across red garnet, usually almandine, pyrope or a combination. Other commonly used varieties are hessionite garnet, a honey yellow to deep brown hue gem; Tsavorite, a gorgeous green color; and demantoid garnet – also a fabulous green, rare and quite valuable garnet. These gems aren’t heat treated; garnet actually takes heating very well without any affect on their appearance. I’ve fired garnets into fine silver Precious Metal Clay – in my kiln at over 1600° F – with no change to the gems at all.

Gem tourmaline is another silicate mineral; like garnet, it also has a different crystal growth pattern and has a different composition. Tourmaline is a very common mineral; some kinds are much more rare. Tourmaline can be very costly depending on the variety and the quality. Black tourmaline is a common gem and is affordable; good quality green and pink tourmaline gems are usually moderately priced. Two color green and pink stones are usually known as watermelon tourmaline. Some tourmalines are irradiated to intensify their color; These are almost always a bright pink tone. Similar to many other gemstones, their color depends on impurities – metals within the crystal mineral; iron, lithium, magnesium, aluminum and copper can all determine the tone of tourmaline. Tourmaline gems are found in a very wide range of colors.

Opal is an unusual silicate mineral. Opal starts to form as a liquid; opal has a high water content and is often called hydrated silica for this reason. Opal gems are often one color, without bright flashes of color displayed in most multicolored opal gems. This “play of color” is a result of the internal structure of the opal; this is a result of how the stone is formed. Silica rich water finds its way into rock cavities and fills them; time passes and as the water dries out, this silica is deposited, slowly accumulating and filling the empty areas in the host rock. This silica is made up of tiny sphere shapes; if the deposited spheres are in a random order the stone is common opal. However, if these spheres are tightly packed in an ordered pattern, gem opal with brilliant flashes of color is the result. Common opal is sometimes called potch; of course it depends on the color, but common opal can be a really nice gemstone. Peruvian pink and blue opals have no play of color but are gorgeous gems, and fabulous orange-red Fire opal from Mexico is popular. In its liquid form – before it becomes opal it can fill in and take the place of organic objects, becoming fossilized; opalized shells and wood are examples of this. Opal jewelry is very popular today, and the availability of these gemstones is excellent. 

Another silicate mineral sometimes colored by impurities, topaz is usually a colorless stone. Most of the topaz used in jewelry has been enhanced by artificial means to give it the beautiful color of these topaz gemstones. Golden toned Imperial topaz has a natural color, but it can be sensitive to strong light and can fade with prolonged exposure to light, particularly direct exposure to sunlight. The blue topaz found in most jewelry today has been irradiated, followed by heat treatment; the intensity of the color depends on the impurities present in the stone. This is usually a permanent enhancement technique; the gem’s color is changed deep within the crystal. New types like Mystic topaz have surface coatings applied with a vapor deposition technique; these treatments hardly go below the gem’s surface, if at all – this means the owner needs to take special care with these gems. The outer coating can easily be removed, uncovering the colorless topaz within; coated topaz should never be steam cleaned or cleaned with an ultrasonic jewelry cleaner.

Another silicate mineral, Beryl is a highly prized gemstone. This mineral can be found in many colors; the most well known are aquamarines and emeralds. Emeralds can be quite high priced and good quality gemstones are extremely rare. Most of the emeralds set in commercial jewelry are very included, and they can have many visible internal fractures that can reach the surface. To fill these cracks and improve the strength of these emeralds, a polymer named Opticon can be used as a surface treatment. Emeralds are also routinely coated with cedar oil. This helps to improve their appearance and makes the imperfections less noticeable. As mentioned above, disclosure of the enhancement is required. However, a lot of retailers just are not aware that they are required to understand how their gemstones are treated, and so they don’t inform the customer at the point of purchase.

Other varieties of beryl one might find set in jewelry are these gemstones:

Aquamarine which is a bluish green hue, and is a lot less expensive than emerald; heliodor, usually a bright golden yellow to green colored beryl; it is also more affordable than emerald. Morganite is a beautiful pink beryl; it is sometimes an irradiated gem. Goshenite is colorless, and most are not very clean; goshenite is usually not very expensive or valuable. Red beryl is an unusual color. It is also called bixbite.

Gemstones in the Feldspar group are popular and used often in jewellery. Feldspar gems include Labradorite, Spectrolite, Moonstones, Sunstone and Amazonite. Feldspar is a common stone family, one of the most common minerals on Earth. When cut properly most feldspar gems show a visual effect; this is called adularescence. The flashing colors in labradorite is an example of adularescence. Oregon sunstone shows a phenomena called the Schiller effect; this is due to copper flakes within the gemstone.

Corundum is an aluminum oxide; this mineral family includes sapphires and ruby. Actually, ruby is the same basic compound as sapphire; rubies are red because of chromium impurities. Only red corundum is a ruby … every other color (and there are many) are all sapphires. Sapphire gemstones can be light or deep blue, white – or colorless, green, pink, brown, black, violet, gray or a pretty golden yellow color or a rare orange shade called Padparadscha. But the most valuable and prized color is called cornflower blue. This mineral is very hard – second to diamond. Corundum abrasives are widely used; emery cloth is a corundum “sandpaper”. Sapphires are normally heat treated to enhance their clarity and bring out their color. Colorless sapphires are sometimes diffusion treated with beryllium to make bright orange tinted “padparadscha” sapphires; however, this is just a surface treatment. Many high end sapphire pieces will be accompanied by a gemological lab certificate that states the sapphires are untreated and natural. Unfortunately treated gems are rarely disclosed; you probably should assume that unless the piece comes with a gemological certificate stating it isn’t treated … it is.

Enhanced gemstones are usually quite beautiful, and they make gem set jewelry a lot less expensive. There is nothing wrong with enhanced or treated gemstones; however, the dealer who sells jewelry containing enhanced gems is required to make this clear. In the U.S., the F.T.C. has a list of guidelines the jewelry industry is required to follow; these rules have been created to guard consumer from fraud. If nothing is said regarding the gems in the jewelry you’re thinking about buying, remember to ask if the jewels have been enhanced or if they’re untreated gems. You have a right to know what you’re buying!

Article ©2010 Written by Bob Edwards, webmaster of a popular retail jewelry website featuring handcrafted gemstone jewelry. Bob is a metalsmith located in NYC with more than 30 years experience in the jewelry business.This article may be published on websites and blogs as content provided all links and this author’s statement remain unchanged.