Monthly Archives: September 2017

Metamorphic Rubies

Some of the world’s most spectacular gemstones were created because of massive geologic events. In South Africa diamonds scattered the surface of the earth and it was later discovered that the source of these gemstones was the mouth of an ancient volcano. Like diamonds, rubies are formed under extreme geologic conditions and forces, they are nothing less than geologic miracles.

About 250 million years ago the super continent Pangea split up to form Laurasia and Gondwana. Laurasia was the upper continents of the former Pangea (now Northern Hemisphere), and Gondwana, the lower continents of the former Pangea (now Southern Hemisphere).

Eighty million years ago the Indian continent broke away from Antarctic and started making its way north from Gondwana into the Northern Hemisphere.  Traveling at the swift pace of 10-12 inches a year, it took approximately 30 million years to travel 4,000 miles north, and in doing so the geologic forces closed the land gap by uplifting and folding the Tethys Ocean floor as it went.  As the Indian continent slammed into Asia it created the top of the world, The Himalayas, with a peak of over 29,000 feet. The tropical, salt water of the (once Tethys Ocean and later) Tethys Sea was rich with plant and animal life, and now their fossilized remains are forever locked in the band of rocks along where the two continental plates collided.

So what does all this have to do with the formation of beautiful, rare rubies? Trace amounts of salt. Ruby is a variety of Corundum. Its chemical composition is aluminum and oxygen (aluminum oxide), and chromium is the element that gives ruby its bright red color.  Some areas of the Tethys Sea were quite shallow and in other places the seawater evaporated entirely leaving behind a rind of salt. In this particular geologic and geochemical environment salt mixed with wash off from the land to form a unique limestone that, once heated, acted as a flux allowing for the aluminum to mix with the chromium, creating very pure rubies with beautifully developed crystals in the metamorphosed marble host rock.

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