Thursday, September 15, 2011

Rock Review: Obsidian

Today’s Rock Review features, the classic Obsidian!
Geology Buzz
Obsidian is a volcanic glass which occurs naturally, making it an igneous rock. Obsidian forms when lava containing the minerals Feldspar and Silica cools too quickly for large crystal formations to crop up. This process leaves Obsidian with its trademark smooth glassy surfaces.
It can be found in lava beds and usually ranges in color from smoky gray to deep jet black. The presence of other minerals, such as Iron or Magnesium can sometimes give the gem a reddish or green cast. A special kind of Obsidian called Snowflake Obsidian can occasionally be found when white crystals inclusions exist, creating a white fractal pattern. When bubbles are trapped in Obsidian, they can leave a golden or iridescent hue in the stone as well producing what gemologist call Rainbow Obsidian. A rare form of weathered Obsidian with a gray opaque band called Apache Tears can also be found on the San Carlos Indian reservation in Arizona. Who knew one gem could have some many different looks!
Fun Facts
People have been making good use of Obsidian since the caveman days, when early cultures used stone fragments for arrow and spear tips and other tools because of its naturally sharp angles when fractured. Greeks and Aztecs also used it as a primitive mirror. Today, we still use Obsidian as a cutting tool on surgical blades since it’s able to cut to a near molecular thinness and has a flat non jagged edge, even under an electron microscope.
Thankfully for those in jewelry business, people somewhere along the way found Obsidian to be ideal for adornment as well as utilitarian purposes. It makes a great beads as well as lovely cabochons. Many wearers enjoy the benefits of its metaphysical properties which include guarding against depression and sharpening insight.
Jewelry lovers who own Obsidian pieces should keep in mind that although the gem is sturdy, it is essentially glass, and therefore needs should be protected from blows that could lead to cracks and scratches and chips. Never clean this gem in an ultrasonic, steam cleaner or chemically based jewelry cleaning solutions. For care and maintenance, a rinse in warm water and polish with a soft cloth will do the trick.

No comments:

Post a Comment