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Obsidian Gemstones - Pure form of glassy rock

Introduction

Obsidian is a natural glass that also goes by the name of Apache Tears. This is said to be the most pure form of glassy rock, which came about because the lava it was formed from cooled down too fast and did not form crystals. This is a mineral that was fittest found in Ethiopia and the name comes from the Roman soldier who first saw it and brought it to Europe.

Some of the specimens may have small air bubbles that did not escape during cooling and these cause the rock to have a golden vitreous luster which can at times appear to look like a rainbow. When you look at snowflake obsidian, it looks like true snowflakes are falling from the sky, and these are due to the patches of potassium feldspar which form the bubbles within it. This is a gemstone that people believe has the ability to sharpen the mental capability of the person wearing it.

In Mexico, during ancient times, people used to make small figurines of their god Trecalipoca out of this gemstone. And in South America, the gemstone was used in the making of mirrors. Obsidian has a black, brown or dark green color, but there are some samples that are transparent. The main places where it is found are Mexico, japan, The United States of America, Russia and New Zealand.

A little more information about obsidian gemstones

This is a variety of glass, as mentioned earlier, and has varieties that go by names such as Apache Tears, Macusanite, Rainbow Obsidian, Snowflake Obsidian, Sheen Obsidian and Mahogany Obsidian. They have an amorphous crystal nature and are normally found as round masses that were thrown out of the volcanoes as small tiny pieces, as fine and hair-like filaments. They also occurs as flows. They are found in the colors of gray, which has bands of brown, and also black. Rarely do you find this gemstone in the color blue, violet or green. Basaltic obsidian has many more varieties and these have the colors of black, brown, blue-green, blue and gray. The gemstone also has some form of iridescence, in the colors of gold, silver, violet, and green and also a combination of all of these colors; the colors are brought about by minute inclusions of air that was trapped in the cooling process.

This is a gemstone that has a vitreous luster and a hardness of 5; Basaltic has a hardness of 6 on the Mohs scale. They generally have a density of about 2.33 to 2.42, but Basaltic Obsidian has one ranging from 2.70 to 3.0. This is a gemstone with a conchoidal fracture and is very brittle. The Basaltic one tends to splitter a lot, so care must be taken when handling the gemstone. There is no luminescence on this mineral.

In general, Obsidian is a very fascinating material, and has a very wide range of varieties, which all look distinctly different. Snowflake Obsidian has got sperullites of cristobalite, and are usually used in the making of cabochons and also beaded jewelry. Another one, Apache Tears, which has got a core that is purely unchanged glass, is found in nodes lying in decomposed obsidian; these are very popular among people who are starting on the hobby of collecting the gemstone. Some of the gemstones are faceted; these are usually the rare red, blue and green varieties. Hobbyists like faceting these rare glass rocks. Since the gemstone is quite soft and sensitive to heat, a lot of care must be taken during faceting. The brittle nature of the gemstone necessitates the use of a lot of care when worn as jewelry. The gemstone tend to look very dark when they are cut into facets, and this is quite unattractive, but when they are cut in small sizes, some of the internal properties come to the light. The blue and green varieties can be cut in large sizes since they have a higher level of transparency.

It is said that a Roman soldier by the name of Obsius is the one who found it in Ethiopia and this is where the name comes from. The mineral is isotropic in nature with a value ranging from 1.48 to 1.51, but normally 1.49. The crystals that are found in the glass may at times no birefringence.

The inclusions in the gemstone are varied and may appear as round bubbles, elongated bubbles that resemble torpedoes. And some have the shape of tears. The bubbles usually are arranged parallel to one another. There are also needle-like inclusions which give the stone a silver sheen on the surface. There are also protogenic traces of silica which crystalize in obsidian, and these can seem like white snowflakes, and this is why this variety is called the Snowflake Obsidian.

This is a mineral that is found in many places on the planet but most of them are found in the United States of America. The gemstones are found in places where there has been volcanic activity either present or past. In Nevada, the obsidian deposits are found mainly in Hawaii; other places are Iceland and Japan. There are some iridescent varieties that come from Oregon. Yellowstone National park in Wyoming also has several varieties. You will also find the mineral in New Mexico, which is very famous for having Apache Tears, and occur as tiny obsidian lumps that have perlite shells. Arizona, Colorado and Californian also have the gemstones in several localities. Utah is the main source of Snowflake Obsidian and in Mexico, there are Obsidian deposits that are famously banded and have a lot of sheen.

Physical analysis of obsidian gemstone

The Key separations of obsidian are the refractive index, specific gravity, and the appearance under magnification and also the naked eye. It also has quite a number of misnomers and it has been called the Fire Pearl, Agni Mani, Glass Agate, Mountain Jet, Montana Jet, Nevada Diamond, Mountain Mahogany, Tokaylux Sapphire, Nevada Topaz and Iceland Agate. It has a transparency that varies from clear to opaque. This is a mineral with a refractive index of 1.49. The mineral is singly refractive when viewed under the polariscope. The fluorescence of the gemstone is generally inert when viewed under both short and long wave ultraviolet light. It does show some pleochroism and has a weak dispersion with a fire value of 0.01.

Chemical analysis of obsidian

This is generally a silicate mineral that contains sodium and/or magnesium. It has an amorphous crystal nature and a hardness value of about 5 to 5.5 on the Mohs scale; it also has a white streak. It is a fairly tough stone

A deeper look at the inclusions found in the gemstone shows that particular ones are found in certain varieties. Cristobalite, stubby needles and gas bubbles are the most common inclusions.

  • Banded obsidian has sinuous or curved bands in the crystal
  • Macusanite is a pale yellow and sometimes greenish variety that is mainly found in Peru
  • Mahogany obsidian has a red or black band
  • Onyx obsidian has straight and parallel bands running across the stone.
  • Sheen Obsidian has a golden or silvery sheen which is caused by gas bubbles.
  • Snowflake obsidian usually has patches made of crystobalite, and these look like snowflakes on a dark night.
  • Rainbow obsidian has iridescent colors that display all the colors of the spectrum
  • Apache Tears has small, irregularly shaped gas nodules that resemble tears, and this is common in the American Southwest, hence the name Apache.
This is a gemstone that has a vitreous luster that can sometimes seem to be greasy. It also has a conchoidal fracture and no cleavage.

A profile of Obsidian

This is a gemstone that is formed as an extrusive igneous rock and has a glassy appearance. When felsic lava is extruded from a pool of volcanic lava, it cools very fast and does not form crystals; this is how obsidian is formed. This is a mineral that is found commonly along the margins or edges of rhyolitic lave flows which go by the name of Obsidian Flows. It is at these edges where you find a lot of silica, and this causes the lava to increase in viscosity and also polymerization. Since the lava here is viscous and polymerized, then there is very little atomic distribution going on here, and this is the reason why the material does not form crystals, like in other gemstones. Although obsidian is hard, it is quite brittle and usually fractures into very sharp edges. This is the reason why this mineral has been used in the making of scalpels and other cutting and piercing tools.

The origin and other properties of obsidian

According to the Obsidian Talus at the Obsidian dome in California, this is among the various forms of glass that are known as obsidian glass, and they are very similar to the stone that was found in Ethiopia by a Roman soldier who went by the name of Obsius.

When you look into the tome known as the English of Natural History, written by the famous Roma Write and gemologist, Pliny the Eder, there are some references in the text that talk about a volcanic glass going by the name of Osian, and this is because the original stone was called the Obsianus Lapis, because of having been found by a Roma soldier and explorer by the name of Obsius in Ethiopia.

Obsidian is a rock that is formed from rapidly cooling lava, the parent material, and it has a very low water content making up for less than 1 percent of the total weight of the rock. However, when the mineral is exposed to ground water, the water content increases, and a perlite is formed in the process. However, very few scientists stick to this hypothesis given that Tektites were also thought to have been obsidian varieties, which were produced by lunar volcanoes.

Although obsidian does resemble a mineral, it is said to be a false mineral, since glass has never been formed through crystallization. It is also said that the composition of the rock is very complex and must have more than a single mineral. This is the reason why the rock is called a mineraloid. This is a rock that is usually black in color, and looks like many other mafic rocks like basalt, but this is a rock that has a lot of iron in it. This is a rock that has more than 70 percent of its weight being formed by silica. Granite and Rhyolite are other crystalline rocks that have the same composition to obsidian. This is a rock that is not very stable on the surface if the earth, and will break down into fine grained mineral crystals. This is the reason why there are no obsidian rocks that were formed before the Cretaceous age, most of them having been broken down, especially where there is water nearby.

Generally speaking, pure obsidian has dark colors, but this may vary when there are other impurities in the rock. The dark color of the rock is due to the presence of iron and magnesium. It is only rarely that you find samples that have a clear color.

A closer look at the occurrence of obsidian

Obsidian is mainly found in areas where there has been a rhyolitic volcanic eruption. These include places like Australia, Canada, Chile, Georgia, Greece, Guatemala, Argentina, Armenia Azerbaijan El Salvador, Iceland, Kenya Japan, Italy, Turkey Papua New Guinea, Mexico, New Zealand and the United States of America.

Other interesting deposits of obsidian include the obsidian flows which people love to hike on, and are in the Newberry Volcano and Medicine Lake Volcano calderas; these are found in the western parts of North America, and also the Inyo Craters to the east of the Sierra Nevada in California. The Yellowstone National Park, has a whole mountainside that is said to contain obsidian and this is found between the Norris Geyser Basin and the Mammoth Hot Springs. There are also other states in The Unites States of America that boast substantial deposits if the mineral. These are Washington, Colorado, Arizona, Texas, New Mexico, Idaho, Oregon and Utah. One can also find obsidian in Virginia, North Carolina and Pennsylvania, which are states found to the east of the USA.

In the Mediterranean, you can only find obsidian in four main laces and these are Monte Arci, Pantelleria, Palmarola and lipari.

In ancient times, obsidian was mainly found in the Aegean, namely Giali and Melos.

In Central Anatolia, the main sources of obsidian are Acigöl town and the Göllü Dag volcano, which are the most important prehistoric deposits in the world.

The historical use of obsidian

It is from the Kariandusi area of Kenya, where you come across the first archeological evidence of the early usage of tis mineral. There are other sites that show that it was used in the Acheulian age, which dates back more than 1.5 million years ago; about 700,000 BC. There are very few objects that were made in this period when compared to those that were made in the Neolithic period. In areas around Lipari, you find many pottery items that were made using obsidian. Archeologists still say that though early, the find is less significant and could only be found in areas that would take about two weeks to journey to.

The Anatolian finds of obsidian objects include those that had been made within the Levant and Kurdistan Iraq. These were made from a period dating back to 12,500 BC. The first civilized use of the rock can be found in the digs at the Tell Brak, which were from about the late fifth Millennia. In the Stone Age, obsidian was mainly valued for making sharp cutting and piercing objects. Like all other natural rocks and glass, obsidian breaks in a conchoidal manner. It can also be polished to a high luster and can fashion mirrors. There is a new way in which archeologists are able to date this mineral and it is called obsidian hydrating dating; this is the only way in which they can tell the true age of artifacts made of obsidian.

In the Middle East, obsidian was used in Turkey, at a place known as Tilkitepe, from as early as the 5th millennium BC, and artifacts from this period can be found at the Museum of Anatolian Civilizations. In the Ubaid, blades manufactured from obsidian, from as early as the 5th millennium BC can also be found, and the obsidian for these came from the current Turkey. Ancient Egyptians are also said to have imported the mineral from the southern Red Sea and eastern Mediterranean regions. Obsidian was used in circumcision rites, because it was light and very sharp. Tools, mirrors and decorative objects were the main uses of obsidian in the eastern Mediterranean region.

In the Gilat areas, which is found I the West regions of Negev Israel, Obsidian objects have also been found. There are eight of these which are said to have come from the Chalcolithic Age, and the objects found were said to have been made from obsidian mined in Anatolia. It is due to Neutron Tracing Analysis of the obsidian traces found in the area that led to the determination of obsidian trade routes and the trading networks that were formed then.

In the Americas, you can find obsidian being used in the making of plates and other items by one Lopez Pelcastre of Nopalillo, Epazoyucan, Hidalgo. These can be seen at the Museo de Arte Popular, in New Mexico. In order to understand the pre-Hispanic groups found in Mesoamerica, one important tool is through Lithic Analysis. This is a method that has been used to reconstruct production, commerce, distribution and of obsidian, and therefore see how the cultures interacted economically. One could tell the social and political life of the civilizations. The Mayan City of Yaxchilan, has been analyzed and one could even tell how they fought their wars depending on the way obsidian was found, formed as weapons. In California, the same technique has been used sat the archeological digs at the Chumash Sites on the coast of California, which show that there was a lot of trade with the Casa Diablo, which is another archeological find in the Sierra Nevada Mountains of California.

The Pre-Columbian Mesoamericans had an extensive and sophisticated use of obsidian, and it was used to make decorative objects and other tools for their work. They also did fashion a sword that would have an obsidian blade that was mounted on a wooden handle. This sword was called a Macuahiitl, and was used to inflict very bad injuries on opponents, since it has a sharp cutting surface, and the edge was also serrated.

Throughout the American continents, the Native Americans used to trade in obsidian, one could find a distinctive type of obsidian at every volcano, and sometimes during different eruptions of the same volcano. This is how obsidian could be traced by archeologists to date the time a particular objects was fashioned. This is the same type of tracing technique that has been used to date obsidian objects coming from Greece, and also the islands of Yiali, Nisyros and Melos in the Aegean Sea. You could also find obsidian objects deep towards the inland, which came from the coast of these islands. For example, one can find objects that were fashioned from obsidian coming from the Ciaten Volcano, at distances of about 400 kilometers at a site known as Chan-Chan. This is an area to the north of the volcano, but there are also traces found about 400 kilometers to the south as well. On the Easter Island, Obsidian was used around the Rapa Nui in the form of sharp tools such as the Mataia. It was also used in the making of the eyes of the Moai statues.

The current use of obsidian

Obsidian is used on humans, although this is something that is still awaiting approval by the FDA. There are some surgeons who are fashioning scalpels out of obsidian. They say that obsidian, when properly cut, will form an incision that is finer than that which could be made from the finest and toughest steel. The scalpels that are made from obsidian have a thickness that is only 3 nanometers thick, which is quite fine.

When the sharpest of all knives is viewed under a microscope, one can still see some jaggedness around the edges, but when a blade made from obsidian is viewed under the electron microscope, it is still smooth in appearance. When a surgical procedure was done on rats, they found that the inclusion found in obsidian lowered the production of inflammatory cells, and there was less granulation in the tissue after 7 days. Don Crabtree has produced many surgical blades for operations and other medical procedures and they have written a lot of material on this topic. However, the blades can only be purchased for the use of research on animals.

Obsidian is also used in the making of gemstones and other ornamental items. Depending on how it is cut, an obsidian will produce different appearances. When material from the same rough is cut in one direction, it will have a jet black color, and when cut in another, it will have a shiny gray appearance. In the early 1970s, the famous audio turntable producer, Technics, used obsidian in the making of their plinths.



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