corundum, Kenya.12, gems

N.R. Barot and R.R. Harding describe a deposit of pink corundum in the eastern foothills of Mount Kenya and examine its geology, production, gemmological properties, and possible relationship to dyed corundum marketed through India. The Taawajah claim in northern Kitui lies within the Mozambique orogenic belt, where Precambrian basement rocks include quartzites, marbles, calc-silicate rocks, amphibolites, and gneisses associated with intrusive rocks. Pink corundum was recognized during prospecting in 1969, but development followed renewed surveying in 1988 and registration in 1989. Open-pit mining employs pneumatic drills, hand tools, washing, sieving, and manual selection, with a workforce of approximately 30–50. Reported weekly recovery generally ranges from 50 to 100 kg and occasionally reaches 200 kg. Most corundum occurs in shallow gravel, while deeper material remains attached to other minerals, suggesting a predominantly eluvial deposit derived from nearby rocks with some local reworking. Most production is exported to India; approximately 1–5% is considered good quality and is cut locally or sold to Germany. The translucent light to medium pink material is principally suitable for cabochons and beads. Examination of rough and polished specimens reveals reddish-pink colour, commonly complicated by red zoning, occasional blue areas grading through purple, iron staining, abundant fissures, twinning, and variably coarse rutile silk. Associated minerals include hornblende, feldspar, quartz, and micaceous material. Untreated specimens show moderate dichroism and orange-red ultraviolet fluorescence, weakened by increasing opacity or blue coloration. Electron microprobe analyses establish minor chromium and somewhat higher iron contents, while ultraviolet–visible spectra show no obvious features distinguishing the material from previously documented ruby and sapphire. The authors also investigate red-dyed cabochons and faceted beads obtained through India. Microscopy reveals patchy concentrations of dye along fractures, with fluorescence arising chiefly from these fissures. Treated cabochons have spectra closely resembling those of untreated Kitui corundum, making Kitui a possible source without establishing provenance. The dyed faceted beads differ spectrally and contain no detectable chromium at the stated analytical threshold; their source remains unknown. Water immersion produces no apparent dye loss, whereas organic solvents cause varying degrees of dissolution. Ethyl alcohol and amyl acetate are particularly effective for detecting dye in the beads through a pink residue transferred to white tissue, although cabochons with fewer fissures may require more persistent examination. The study documents a commercially productive source of cabochon-grade pink corundum and demonstrates the importance of fracture inspection and solvent testing when assessing strongly red material that may owe its appearance to dye.