Jegdalek ruby is the gem-trade designation for ruby produced from the Jegdalek deposit in Sorobi District of Kabul Province in eastern Afghanistan, located approximately seventy kilometres east of Kabul. Jegdalek has been worked for ruby and pink spinel for at least one thousand years and remains a small but continuing producer of fine ruby material with characteristics distinctive enough that origin determination by major laboratories is reliable for stones of typical Jegdalek character.

Geology and Mineralogy

Jegdalek ruby is hosted in marble units of metamorphic origin, in the same broad geological setting as the rubies of the Mogok stone tract in Burma and several other historical Asian deposits. The host marble formed during the Indian-Eurasian continental collision that has also produced ruby, spinel and lapis lazuli at related deposits across the Pamirs and the Hindu Kush.

Colour and Character

Jegdalek ruby is typically a medium to dark red, sometimes with a slight pinkish or purplish modifier, and the strongest material can compete in colour with lesser-grade Burmese ruby. The material exhibits strong red fluorescence under ultraviolet, consistent with its low iron content and marble-hosted character. Inclusion suites characteristically include rutile silk, calcite crystals, fingerprint healing fissures and characteristic growth zoning that is among the diagnostic features used in laboratory origin determination.

Crystal Sizes and Production

Crystals are typically small, with finished cut stones above two carats already relatively unusual and stones above five carats exceptionally so. Production is artisanal and small-scale, with modest annual volumes flowing through Afghan and Pakistani dealer networks and on to the international cutting centres in Bangkok and Jaipur.

Treatment

The bulk of Jegdalek material in commercial trade is heat treated to improve colour and clarity, in the manner standard for ruby of this type. Untreated Jegdalek ruby of fine quality is rare and trades at a substantial premium relative to comparable heated material.

Identification

The major laboratories including GIA and the Swiss laboratories provide origin determination for ruby and routinely distinguish Jegdalek material from Burmese, Mozambican, Thai and other sources on the basis of trace-element chemistry, particularly the iron, gallium, vanadium and chromium ratios, in combination with the inclusion suite. The combination of low iron, distinctive Mg-rich inclusions and the characteristic fluorescence behaviour gives Jegdalek a relatively recognisable laboratory signature.