Pakistan Ruby: Gemstone Information
The Pakistan ruby deposits are associated with the Karakoram suture zone, the stones occurring in metamorphosed recrystallized dolomite marble in a narrow belt extending from the Hunza valley to Ishkoman, a distance of more than 100 km. Crystals are well formed and range from pink to a fine red. Included material is cut into cabochons but some of the finest reds are high facet-grade.
Other mineral inclusions were dolomite, the potassium mica phlogopite which occurs as reddish brown flakes and feather-like greenish crystals of the calcium mica, margarite. Pyrite, pyrrhotite and apatite were also found. However, no trace of rutile has yet been reported so that no Pakistan star rubies are likely to occur (so far). The absence of rutile is of course useful in the diagnostics of locality. No sapphires have yet been reported from Pakistan. Some Pakistan rubies show a distinct phosphorescence following X-ray irradiation, a phenomenon most commonly seen in some synthetic rubies.