Gemstones

A gemstone is either organic (meaning it was made from a living thing like coral, pearls, or amber) or inorganic, which means it was made from minerals. Out of the more than 3000 minerals discovered so far only about 100 of them qualify as gems.

Most colored stones form in the earth's continental crust. Every time heat and pressure force rocks to change (as in igneous,metamorphic and sedimentary rocks) there is potential for gem formation to take place. Many gemstone deposits have been found in areas around mountain ranges for this reason. Most of the world's ruby, emerald, topaz, garnet, and tourmaline form in the heat and pressure of the mountaing building process.

Heat and pressure? What does that mean? Take your hands and push them together and move them back and forth at the same time. Do you feel the heat? That is how the earth's plates react when they move. The pressure and the movement of the plates create heat, which melt the minerals in that area. If the right minerals are present in the right amount a gemstone could possibly form. As the hot mineral liquid cools it forms crystals. If the mineral liquid cools quickly closer to the surface of the earth, many small crystals will form. If the liquid cools slowly deep within the earth, large crystals will form. So, now that we have a gemstone crystal how do we get it out of the ground? Read on my friend!

Mining takes place one of two ways, either by high tech mechanized mining with lots of expensive equiptment or by getting dirty and digging with small inexpensive tools like shovels. While almost all diamond mining happens with the expensive equiptment, most colored gemstone mining happens with a good ole shovel and a pan (much like panning for gold). Why? Well, there are several reasons. One is that as awesome as colored stones are they just dont produce the kind of money that diamonds do. Colored stone mining isn't a big production like diamond mining. In diamond mining entire cities need to be built around the diamond site to support the workers and their families that work there because usually the diamond mine is in the middle of no where.

Another reason why colored stones are mined with primitive tools is that they are usually found in alluvial deposits while diamonds are usually found in eluvial deposits.

What in the heck does that mean? Well, picture the gemstones lying quietly in the ground, way below the earth's surface when something happens, pressure builds up creating a kind of explosion that forces the gems out of the ground and flings them in the air. Some gems (and diamonds) and dirt and debris fall back into the hole that was created from the eruption. This makes the hole almost impossible to see. It might look like a dip in the ground miles long and if it rains alot it can even turn into a lake. This is now an eluvial deposit. In order to mine this hole effeciently you will need to use heavy machinery to be able to dig down deep to get the gems out. This is how most diamond deposits are mined. Now during that eruption many of the stones didnt fall back into the hole but were thrown in many different directions around it. It was then transported further away by rain or by rivers depending on where it fell. The deposit of stones that were transported away from the original rock they were formed in is called an alluvial deposit. These stones, especially the ones that are found in rivers are usually very beautiful and durable because they've had a rough ride and any weak part of the stone has already broken off. Alluvial deposits are often mined by people working from sun up to sun down in intense heat trying to find gemstones to support their family.

Once the gemstone rough is pulled out of the ground it is sold and taken to a cutting center. India cuts more gemstones than any where else in the world.

The gem cutter first decides if the piece of rough will become one stone or two. Then he devides the rough into sections and gives the stones their partial shape. This is called "sawing". The next step is called "grinding". The rough is prepared for faceting. It is ground to its partial shape and proportion, including its table facet, crown and pavilion.

The stone is then faceted. There are three different styles the cutter can chose from:

Briallant cut - this is the most popular. It is used on rounds, pear and marquise shaped gemstones. It consists of kite shaped facets.

Step cut - rectangular facets that are cut below the table and run parallel to the gemstones girdle. They have less facets than a brilliant cut. Emerald cuts are step cuts with their corners cut off.

Mixed cut - both the brilliant cut and step cut is used.

One other type of cut is called the fancy cut. This is usually used for large and/or valuable stones. The cutter will chose an unusual shape to retain as much of the stone as possible. Also some gemstones are cut in the shapes of animals and other objects.

Heat treatment is an age old process that is still used today. 95% of sapphires and almost all tanzanites are heat treated. Zircon, topaz, aquamarine and amber are also heat treated. Heat treating a gemstone can add color, remove color or change color. Most of the gemstones you will ever come in contact with are heat treated and can greatly increase the stones beauty and is most often permanent.

Most consumers dont mind if a gemstone is heat treated. They understand why it was done and appreciate its beauty. The problem that arises is when this treatment is not disclosed. Some consumers feel cheated or lied to when they find out later their stone was treated without their knowledge. When you buy a gemstone you can assume that the stone was heat treated. Anytime I buy a gemstone I always ask what kind of treatment it has received. Any honest jeweler will tell you.

There are other kinds of treatments out there that also make stones more beautiful and durable. These treatments should always be disclosed. Sometimes the other treatments are not as permanent as heat treating and can come with a list of precautions for wear and cleaning.

A common treatment for emeralds is fracture filling and oiling. The treatement is also used for other stones. The gem's fractures (sometimes called fissures) are filled with a colorless substances like colorless oils, resins, glass, and polymers. Using oils is a centuries old practice and despite the concerns over durability it's still very common. Unlike the other fracture filling treatments, oiling is usually reversable. Emeralds should only be cleaned with a mild soap and water. Ultrasonic cleaners can remove the substances used to filled the fractures.

Other treatments include irradiation (exposing a gem to radiation to change or improve its color), dyeing, bleaching, sugar and smoke treatments (used to enhance the color and fire in opals), lattice diffusion (the gemstone is heated to close to its melting point and color causing minerals are added which change the color of the gemstone). All of these treatments should be told to the consumer.

Ruby - Color is the most important factor in determing a ruby's value. Color can range from orangey red to purplish red. The finest ruby has a pure, vibrant red to slightly purplish hue. Ruby is variety of the gem species corundum (as is blue and all colors of sapphire). In it's purest form corundum is colorless. Chromium causes ruby's color. The most beautiful rubies, like those from Myanmar, the Himalayas and northern vietnam, typically form in metamorphic rocks like marble.

Almost all rubies are heat treated. Heat treating rubies can improve color by making it a more intense red. Thailand is the biggest supplier of rubies to the United States with India coming in second. The US imports more rubies than any other country.

Blue Sapphire - The most highly valued blue sapphires are a velvety blue to violetish blue color. Iron and titanium cause blue sapphires color. 95% of blue sapphires are treated. Heating and lattice diffusion are the most common kinds of treatment. The United States is the biggest market for sapphires where half of the world market is sold to US buyers. Most of the world's faceted commercial quality (the ones you find in department stores and most jewelery chains) are from Thailand. Montana also produces blue sapphires. Stones from Yugo Gulch Montana are not heat treated. They are small but have beautiful color. Other mines in Montana produce stones that dont have as good of color and are heat treated.

Emerald - The most valued emerald color is bluish green to green. Chromium, vanadium and iron cause emerald's color. More than 90% of emeralds have fractures filled with oil or resin. An untreated emerald can be up to 50% more valuable than a treated one.

The United States and Japan account for 75% of emerald purchases world wide. Columbia, Zambia, Brazil and Zimbabwe supply the majority of emeralds. Columbia is the source of the highest quality and the highest volume of emeralds.

Sapphires come in many different colors. One of the most popular fancy colored sapphires is pink. Pink sapphires get their color from chromium, the same trace element that ruby gets its color from. Highly saturated pink sapphires (where the color is a very vivid pink) is a highly rare and prized gemstone. Magok, Myanmar produces pink sapphires that are among the world's finest.

One of the most valuable sapphires is the padparadscha. This stone is an amazing pinkish orange color. It gets its name from the lotus flower. They typically have the highest per-carat value of all the fancy sapphires.

Australia produces some the world's best yellow and green sapphires. Yellow sapphires are usually more marketable than green.

Purely colorless sapphire, also called white or "Leuco", is very rare however it can sell for less than $10 a carat wholesale. The demand for black sapphires is very small and can cost less than $1 a carat.

Purple sapphires are often heat treated to produce a more valuable pink or red color.

Natural pearls form when a foreign object gets inside a mollusk and irritates the soft tissue or "mantle" that lines the shell. The mollusk coats the irritant with layers of nacre (nay-kur). The nacre is made of microscopic platelets of aragonite and conchiolin (kon-ky-uh-lin) which is a binding agent that is similar to material found in our hair and finger nails.

Freshwater and saltwater cultured pearls form the same way but this time the farmers do the work of nature by surgically implanting an irritant (a piece of mantle tissue from a donor mollusk). The host mollusk forms a pearl around each individually implanted mantle tissue piece.

In both cases, both natural and cultured, the mollusk continues to layer the irritant with nacre. The longer it is left alone the larger the pearl will be.

There are four major types of cultured whole pearls:
1) Akoya -Produced in Japan, China and Vietnam. They are usually very round and are white with rose overtones and excellent luster.

2) South Sea -Produced mainly in Australia, Indonesia and the Phillipines. These pearls have a soft, satiny luster unlike the Akoya which has more of a mirror-like surface.

3) Tahitian - Their unusual colors (called peacock - dark green grey to blue grey color, aubergine - dark greyish purple, and pistachio - yellowish green to greenish yellow) demand high prices. They are produced in French Polynesia and the Cook Islands.

4) Freshwater - Mullusks that produce freshwater cultured pearls are called mussels. China produces the majority of these pearls but small crops are also produced in Japan and the United States.

Luster is very important for pearls. It is caused by light traveling through the translucent layers of the nacre and reflecting back to your eye. It's thickness, degree of translucence and the overlapping layers of nacre all contribute to luster.

The word jade is actually a generic term for two different mineral aggregates - Nephrite and Jadeite.

Jadeite is the more commercially valuable of the two gems. It's most desirable color is green but it comes in many different colors. Lavender is jadites second most valuable color. One of the rarest colors is imperial green jadeite. The finest quality jadeite is usually cut into cabochons (a stone with a rounded top and a flat bottom).

There are many kinds of jadeite treatments. Jadeite can be dipped into melted wax to improve its luster and to fill surface pits and fractures. This is extremely common and doesnt affect its value. It can also be soaked in hot hydrochloric or sulphuric acid. This makes it brittle so it is then coated with paraffin wax or a clear polymer resin. This greatly drops the value of the stone. Sometimes jadeite is also dyed. The dye can fade overtime. Heat treatment can also be used and is permanent and undectable. Treatments should be disclosed to you the buyer.

The main source for most top quality jadeite is Myanmar. It's often called "Burmese Jade" after the country's former name.

Nephrite is a lowered price alternative to jadeite. It is readily available but its greens aren't as vivid as jadeite's. Polor Jade, found in 1995 in the Polar Mine in British Columbia, is the brightest, greenest, hardest and most translucent nephrite ever discovered.

Precious opal forms in desert areas that get heavy seasonal rainfall and have rocks that are rich in silica (like volcanic ash and sedimentary rocks). During winter heavy rains falls and rain water trickles down through the rocks and carries the silica from the rocks down with it. The water and silica fills fractures and cavities in the rocks below. In the summer the sun dries the ground and the water evaporates. It leaves the silica in place adn gem opal deposits form. This process takes place of millions of years.

There are two classes of opal: precious and common. Precious opal dispays "pay-of-color" and common opal doesnt. Play-of-color are those brightly colored flashes you see in some opals.

How does play-of-color happen? Precious opal is made of billions of uniform, tiny silica spheres that are all stacked in an orderly fashion. When light waves travel between these spheres the waves bend (defract) and as they bend they break up into the spectral colors that you see.

There are many different kinds of opal: Black opal, white opal, crystal opal, water opal, boulder opal, and fire opal. Black opal is the most valuable of all opals.

Another kind of opal is called an assembled opal. It consists of precious opal layers or layers of precious opal and other material cemented together by man (or woman) to improve to opals appearance and durability. There is also an assembled opal called "mosiac opal". Here pieces of opals are cemented to a dark back ground (usually black onyx) and have a clear material over it (sometimes clear quartz). These can also be called opal doublets or opal triplets, depending on how many layers have been put together.

There are two main kinds of treatment for opals that darken the background color which intensifies the play-of-color: sugar treatement and smoke treatment.