Obsidian

by Oraia Helene

In this article we’re going to take a look at obsidian, or volcanic glass. If you’re like me, you probably think of obsidian as black, but it can also exhibit shades of brown, gray, and even green. It can be transparent to opaque, and has a vitreous or glassy luster.

The name obsidian was given to the stone by the Roman historian Pliny, in honor of another Roman, named Obsius, who apparently found it in Ethiopia. So it basically means “Obsius’ stone,” making it one of the earliest examples of naming a stone after its discoverer that I’m aware of.

It has a hardness of 5 to 5.5 on the Mohs scale, and conchoidal fracture, which means that it doesn’t break along any particular lines; in obsidian, you’ll sometimes see radiating, almost circular fractures that appear to ripple outward from a central point. This type of fracture is what allows for knapping, aka flintknapping, a method of shaping stone that relies solely on the pressure applied to it, not to the internal structure of the rock. When shaped in this way, obsidian can form very sharp edges, which has led to its use in both tools and weapons since prehistoric times.

Obsidian is an extrusive igneous rock, meaning that it is formed on the earth’s surface from molten rock. (As a side note, intrusive igneous rocks, which are formed beneath the surface, are called plutonic, while extrusive igneous rocks are called volcanic.) By forming above the surface of the earth, extrusive igneous rocks cool much more quickly, leading to little or no crystallization. Obsidian in particular usually forms when lava comes into contact with water, leading to very rapid cooling.

The composition of obsidian is mostly silicon dioxide, SiO2, which you may recall is the same as our good friend quartz. But obsidian doesn’t have the crystalline structure that quartz does — plus the silicon dioxide only makes up 70-75% of the rock, while the rest of its composition varies. Iron and magnesium impurities can lend it a dark green or brownish hue; the name mahogany obsidian is often applied to the brown variety, or to blends of brown and black obsidian. Inclusions of white christobalite give us the variety known as snowflake obsidian. Obsidian can also contain bubbles beneath the surface, trapped into particular patterns as the lava flowed and cooled; these bubbles then produce the surface sheen of rainbow obsidian and golden sheen obsidian.

Obsidian is usually found in masses, and sometimes in layers between other forms of volcanic rock. Rounded nodules called “Apache tears” are pieces of obsidian that have been weathered into a rounded shape, and obsidian is also sometimes found in long filaments, known in Polynesian cultures as “Pele’s hair.” Because it is a glass, without a crystalline structure, its edges can get much, much thinner than material with a more rigid structure.

Obsidian arrowheads and knife blades have been found around the world, and its use dates back to the Stone Age. (Apparently there is at least one company currently making surgical scalpel blades out of obsidian as well!) What’s cool is that obsidian from a particular volcano can be identified, so the source of various ancient artifacts can be determined, and used to understand trade routes and supply lines in various cultures. Since obsidian was so useful as material for weapons, ornaments, and polished mirrors, it was widely valued as a trade commodity as well.

According to George Frederick Kunz, the ancient Aztecs used polished obsidian mirrors for divination, and he suggests that John Dee used one of these mirrors in his own scrying work. Dee’s mirror is said to have originated in Mexico — the British Museum website says that it was one of many cult objects brought back from the conquest of Mexico. The Aztec god Tezcatlipoca, whose name means “shining mirror,” was associated with mirrors, and also the subject of devotional objects made of obsidian.

The use of obsidian mirrors for scrying continues today, of course, though not all black glass scrying mirrors are made from obsidian. Spheres and polished eggs of obsidian can also be used as gazing stones; I have a nice rainbow obsidian egg that is very nice for this purpose. Metaphysically, obsidian is most often said to be a grounding and protective stone, and the protective qualities in particular resonate strongly with me, perhaps because of its historical use as a material for weapons. Its reflective nature also suggests its use as a shield against unwanted energies. The mirror-like quality of obsidian, however, can also show us the truth about ourselves, whether we want to see it or not, and its sharp cutting edge can aid in discernment as well, helping us to cut through illusion.

A quick survey of the books available to me indicate no particular agreement on the additional metaphysical properties of the different varieties, like snowflake obsidian and rainbow obsidian. Rainbow obsidian has always been a favorite of mine, though, and I find that it lifts my spirits when I wear it or hold it. Just be aware that if you’ve got a natural piece of obsidian, one that isn’t polished, it may have very sharp edges — it’s glass, after all, so watch your fingers!

This article was adapted from the Terra segment of Media Astra Ac Terra Episode #27.

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