I recently attempted to contact Addison Rice about her article on the origin of sapphires. Unfortunately, she is no longer with the IGS, having decided to pursue a PhD. The editors recommended that I post my question, as there are geologists on this website.
Here is my question:
Igneous rock hosted sapphires, especially yogo gulch have controversy as to their origins. The rock hosting the yogo gulch sapphires is a lamprophyre, an unsaturated, mafic to ultramafic rock which is uncommon. The Argyll diamond mine in Australia is also lamprophytic… the only non Kimberltici source of diamonds world wide…Some theories state that the parental magma of the lamprophyre crystallized corundum. Other references state that they are xenoliths from a deeper source magma. Further references are to basaltic hosted sapphires in Australia and the southeast margin of the Pacific…either way, both the pressure at depth and an abundance of carbon dioxide should be necessary for the formation of lamprophyres, lamproites, kimberlites, and particularly carbonatities…If there are petrologists out there, please commment.
PS: gemstones are the flowers of the crystal world. I am only an amateur geoscientist, which is why I am posing this question to the general audience. My interest is deep earth processes, igneous petrology and how gemstones are formed, more than their valuation and jewerly interest. I have been a jeweler also, as a home hobbyist. Now I am most interested in the deep science behind gemstones.
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