Obsidian is a glass-like mineral produced by volcanic flows. Many types of Obsidian are used as gemstones in jewelry, and some are quite rare and valuable. A fantastic variety of colors and patterns are available.
This stone has a long history as both a gem, and as a utilitarian material for creating cutting instruments. Obsidian was also used in many ancient cultures for creating mirrors, mosaics, statuary, inlays, vessels and other luxury items.
Obsidian is chiefly composed of silica (65 - 70 percent), together with a significant amount of various impurities. It is these impurities which are responsible for the various colors and patterns which distinguish the more valuable varieties. Like glass, it is an amorphous solid - that is, the volcanic material cooled too rapidly for crystaline structures to form.
Some Obsidian contains trapped gas bubbles. These are sometimes stretched into threadlike inclusions. Examples are also known which contain visible bubbles that hold water. Yet others have various other minerals mixed into the stone.
Obsidian is found in volcanically active regions worldwide. Important sources for gem varieties are located in Italy, the Caucasus Mountains (Georgia, Armenia, Russia), Mexico, Italy, and the western United States. The world's largest Obsidian flow is located at Newberry National Monument, in Oregon.
Forms found in the marketplace...
Americanite or Columbianite - a grayish-pink variety from Columbia.
Apache Tears - small transluscent to transparent nodules of brownish color, found in Arizona in Pumice/Perlite deposits. These stones are usually offered tumbled smooth, due to the difficulty of cutting with saws or other tools.
Apache Tears, Rough and Polished (Arizona)
Banded (aka Onyx) Obsidian - applied to varieties exhibiting stripes of different colors.
Burns Green - an opaque form found near Burns, Oregon. The color is generally a mossy green, some of which contain areas of aqua. Many examples display a velvety sheen. Burns Green is a rare variety which sometimes appears in high end items and collectors' pieces.
Fire Obsidian - an ultra-rare, expensive variety from Oregon which has extreme, multi-color flashes in layers. The colorful effect is sort of a cross between a Black Opal, Spectrolite and Fire Agate - though the material is much rarer than any of these. Usually made into cabochons, but also occasionally seen in high-end flaked collectors' arrowheads and blades. Mahogany and Sheen types are sometimes mistakenly labeled as "fire obsidian" - make sure that the photo shows the more colorful rare variety when you encounter a listing for Fire Obsidian.
Precious Fire Obsidian Cabochon
Flower Obsidian - a variety of Snowflake Obsidian in which the crystals have coloring (due to mineral staining or minerals present in the obsidian itself). See the Snowflake Obsidian topic below.
Leopard Skin and Lizzard Skin - multi-colored, mottled types, usually reddish-brown, brown and black.
Mahogany Obsidian - reddish orange to reddish brown streaked with black. Some of this resembles wood grain or burl and others have bolder patterns. All of it is spectacular.
Marskanite (or Marekanite) - a gray to gray-brown variety from Siberia.
Midnight Lace Obsidian - shows a mixture of black and clear layers in a somewhat contorted, lace-like pattern. Some Lace Obsidians contain multiple colors.
Lace Obsidian (Oregon)
Peanut Obsidian - a somewhat rare and unusual grayish Obsidian from Mexico which contains round, orange to reddish-brown inclusions (composed of Labradorite and Iron) which appear as spheres radiating lines.
Pitchstone - this variety has a dull surface, due to the growth of small crystals which form as the Obsidian begins to degrade (i.e., either through great age, or because the molten stone did not cool as quickly as do other Obsidians).
Pumpkin Obsidian - an orange-brown, sometimes mixed with streaks of black or other color
Red Obsidian - this term usually refers to Mahogany Obsidian which is a reddish brown. A fairly strong red variety is known from Mexico, though fairly rare. Colored glass or treated (remelted and enhanced) manufactured reds are also seen being sold as "natural" Obsidian.
Sheen Obsidian - this is a family of valued types which consists of sub-types categorized according to the effect or color displayed. Microscopic bubbles and/or crystals of Feldspar or Mica trapped in the Obsidian result in a chatoyant (irridescent) sheen when the stone is viewed from certain angles.
Golden Sheen Slab (Oregon)
There are several types. As gemstones, these are usually cut into rounded cabochons or carved to show the optical effect to advantage. They are also occasionally found in high-end knapped arrowheads and blades. The background can vary in color from black to brownish with the glow flashing across the surface as the stone is turned in the light...
- Golden Sheen or Cat's Eye - reddish to gold, metallic flash. This variety is often seen in stones which have a brown or mottled brown and black background. When properly cut, it makes a very interesting display.
- Green Sheen - olive-green to slightly sea-green irridescence.
- Plum Sheen - rose to reddish-purple glow.
- Rainbow - layers of differently colored sheen are exposed by careful cutting. Quality stones come from Mexico, California and Oregon.
- Peacock - similar to Rainbow, but somewhat softer and usually with a less glossy polish
- Royal Blue and Royal Purple Sheen - this particular variety is from California, and the colors in good quality stones can be quite intense.
- Silver Sheen - silvery gray shimmer which, in the more desirable specimens, displays an almost metallic effect.
- Velvet - microscopic bubbles give the stone a matte surface (California and Mexico) in several shades.
Carved Rainbow Obsidian (Mexico)
Snowflake Obsidian (aka Flower Obsidian) - the snowflake (or flower) pattern is caused by areas of the glass which have begun to crystalize during the cooling process. These crystals can range widely in size.
What to look for...
- For most types of Obsidian, the quality of cutting is very important. The polish should be flawless.
- Carved pieces should be well-executed with no cracked, chipped or unfinished areas.
- Colors and patterns should be strong.
- Flaked articles (arrowheads, knife blades, etc.) should have a pleasing shape and good flaking pattern.
- For sheen and rainbow stones, the cutter should have selected for the best display. Poor orientation can ruin the sheen and color display.
- For patterned stones, look for a pleasing pattern which is well defined and well finished.
- It is often useful to see photos of backlit stones. This should show any translucent or transparent areas particularly for types (such as Midnight Lace) where transparency is an important part of the pattern. If no backlit photo is available, ask for one.
Things to be aware of...
It is, unfortunately, common to see man-made glass being sold as natural Obsidian. There are also some manufactured stones which have been produced from re-melted or artificially enhanced volcanic material.
Transparent blue, red, yellow and green forms of Obsidian are known. However, such items sold as Obsidian nearly always turn out to be manmade glass or some other mineral entirely. Be suspicious of highly transparent forms, unless the mine is identified and known.
Natural transparent Obsidian usually occurs as small bands or layers, and not as large lumps or uniform pieces. Transparent colored forms seldom exhibit highly saturated, even color. And Obsidian never is found as crystals (so-called "natural crystals," scepters, similar items are sometimes seen being sold as such). Large sculpted pieces, spheres, cabochons, chunks and some faceted pieces which are made from highly colored, transparent material are undoubtedly manufactured glass. Supposedly natural transparent Obsidian (including the so-called "Andara Obsidian") in vibrant blues, greens and reds are often said to be from mines located in China, Tibet, Africa, Italy, Indonesia, California, and elsewhere. But these have tested as man-made in the past, and verification of any such deposits has never been made by independent geologists.
Artificial gemstones created from mixtures of volcanic ash, glass and other minerals, are sometimes found being sold under names such as Helenite, Emerald Obsidianite and Mount St. Helen's Stone. Obsidian-like materials have also resulted from industrial operations and accidents (such as the swirly blue Tengizite "Obsidian" from Kazakhstan), where glass, sand and other materials have melted under high temperatures. These also are sometimes cut for use as gemstones. It is, unfortunately, not uncommon to find these listed as natural Obsidian, though some sellers are scrupulous about noting their true origin. Mottled and opaque slag glass is also seen which is being sold as natural Obsidian.
Occasionally, Basaltic Glass (Sideromelane and Tachylyte) is labeled as Obsidian. This is a different material. Tektites (such as Libyan Desert Glass) are sometimes also mistaken for Obsidian. Both of these types are relatively rare on their own, and mostly of interest to collectors (though some Tektites such as Moldavite are used in jewelry).
Obsidian is a relatively soft gemstone (5 to 5.5 on the Moh's scale). Because of this, it will eventually scratch if used in high-wear jewelry items such as rings or bracelets. Care should be taken in storage, as contact with harder gemstones will also cause scratching or pitting.
Broken or flaked Obsidian can be extremely sharp - Obsidian was used for blades, scrapers, spear tips and arrowheads by many cultures. It is used for surgical and microscopic cutting tools. Be very careful handling chipped shards. - better yet, don't wear Obsidian in pieces that will get knocked about.
Clean Obsidian using warm, soapy water. Avoid abrasives, chemicals, ultra-sonic cleaners and heat, as all of these can harm or even shatter Obsidian stones.
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