Abstract
Corundum and ruby occur sporadically in the soil horizons around Kermunda area, which is situated in Kalahandi district of Odisha. The area is constitutes a part of the Precambrian khondalite-charnockite-granite gneiss terrane of Eastern Ghats. Corundum is light pink while ruby is rose red, carmine or purple red in colour. The corundum and ruby grains contain inclusions of rutile and zircon and are often surrounded by dark coloured spinel exhibiting corona texture. Sapphirine occurs as rim around spinel as well as corundum. Veinlets of hematite and diaspore traverse spinel and sapphirine aggregates. SEM-EDS analysis indicated that (i) corundum and ruby grains contains trace amounts of Fe and Cr, (ii) spinel is pleonaste and chromium pleonaste types and (iii) sapphirine is silica- poor and magnesian rich. The corundum-spinel intergrowth showing corona texture suggests that under high P-T gradient in granulite facies metamorphism, corundum reacted with either phlogopite or garnet to form spinel by the reactions: (i) Corundum + Phlogopite= Spinel + K-feldspar + Water or (ii) Corundum+Garnet = Spinel. Sapphirine is possibly a reaction product of (i) Corundum+Spinel+Garnet= Sapphirine or (ii) Spinel+Silica= Sapphirine.
Highlights
Gemstones, especially the quality gemstones are most sought after minerals throughout ages due to their astrological and ornamental importance
We report macroscopic and microscopic textures and mineral chemistry of eluvial corundum/ruby grains from Kermunda area
The colour of the ruby grains is red to crimson red
Summary
Especially the quality gemstones are most sought after minerals throughout ages due to their astrological and ornamental importance. In India, Odisha state is famous for occurrences of varieties of gem stones and among them ruby and sapphire are conspicuous. The entire resource of ruby (5348 tonnes) is located in the state of Odisha, mainly in Kalahandi and Nuapara districts [1]. The important localities of corundum and ruby bearing zones are Jhillngdhar, Hinjlibahal, Banjipadar and Kermunda in Kalahandi district and Sinapalli and Sardapur in Nuapara district. At Jhillingdara, Mishra and Mohanty [2] reported occurrences of ruby and corundum mineralization at the contact between metapyroxenite and granite gneiss and eluvial placer ruby in the surrounding soil horizons. Mazumder and Mathiew [3] reported corundum (ruby) crystallization in the brecciated pegmatite at contact zones of granite gneiss of Bastar craton near Sardapur area
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