Ruby with sapphire core
There are two basic kinds of corundum, basaltic and metamorphic, with the most beautiful stones coming from marble hosted deposits in the Himalayas and its fringes. Localities such as Jegdalek in Afghanistan, Nepal, Mogok and Mong Hsu in Burma and Luc Yen in Vietnam all result from the metamorphosis of Tethyan limestone that were pushed up into mountains and transformed by the pressures accompanying India’s slow motion ongoing collision with Eurasia.
As gems grow, they tend to do so in fits and starts, depositing new layers on pre-existing seed crystals as and when the conditions are appropriate. In this case it involves the concentration of aluminium from the changing limestone, along with minor trace amounts of the impurities that colour corundum. However conditions may change during one of the pauses in crystal growth, and it is not uncommon to find crystals such as this one from Gamesh Himal in Nepal (2.3 x 1.1 x 1.0 cm), where a blue/purple sapphire core has been overgrown by a later generation of ruby.
Blue sapphire is coloured by a complex electronic interchange between iron and titanium in the crystal structure, while ruby gains its fiery hues from chromium. The type of impurity present in the parent medium changed between the two generations of corundum, creating this unusual visual effect. Such stones are commonly heat treated to remove the blue component, particularly the production from Mong Hsu where nearly all the stones exhibit this phenomenon. I also own a sample like this that I bought in Luc Yen in Vietnam some years ago.
Image credit: Joe Budd/Rob Lavinsky/iRocks.com
Rexroth once said, “I have always felt I was most myself in the mountains. There I have done the bulk of what is called my creative work. At least it is in the mountains that I write most of my poetry… There whatever past emotion and experience I choose to recollect and write down, take on most depth and meaning.” [Read More Here]
Cantabile in B flat - Frédéric Chopin
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Albert Camus, The Stranger