Burmese Rubies - page 2
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Identifying Sources among Burmese Rubies
Nayaseik Rubies
The Nayaseik and Tanai ruby deposits are in the Kachin State in northern Burma. Stones rarely have silk or feathers and are usually very transparent. Inclusions are common, dominated by calcite, dolomite, apatite, and micas as euhedral to subhedral grains with distinct faces. Very small distinct rutile grains have been observed. Typical colors are pinkish red; very few of the prized deep-red rubies have been found.
Nayaseik-1: Subhedral to rounded inclusions of carbonate (calcite?) in pinkish stones with thin, patchy silk are typical for the locality [Frame is 3 mm wide.]
Nayaseik-2: Several large subhedral inclusions of calcite(?) are visible; lower one with reflecting crystal faces indicate a carbonate, probably calcite. Minute patches of thin silk appear at left. [Frame is 3 mm wide.]
Nayaseik-3: An unusual stone with a broad patch of silk and a large rounded inclusion of calcite(?). [Frame is 3 mm wide.]
Sagyin Rubies
Rubies were mined at the Sagyin stone tract from colluvial deposits weathered from marble during the reign of King Thibaw (1878-1886). Color varies from pinkish- to medium-red, although a few stones of intense deep red color have been reported. Stones are relatively free from silk but may contain dustings of rutile particles and transparent calcite inclusions of subhedral to rounded form. The ruby crystals are tabular prisms with triangular growth hillocks on the pinacoids.
Sagyin-1: Rounded inclusions at center are surrounded by very fine and thin oriented silk. Euhedral inclusions to lower right are a single inclusion duplicated by reflections off facets. [Frame is 3 mm wide.]
Sagyin-2: Rounded inclusions of calcite in pinkish stones with minor or no silk are typical. Source of turbidity is a fracture below that is out of focus. [Frame is ~2 mm wide.]
Katpana
Katpana rubies range from purple-pink to pinkish red, less desirable colors in Myanmar. Dense zones of silk are common, yielding many fine star rubies, so the material is mostly cut as cabochons or, alternatively, as small stones for earrings. Sorry, no photographs.
Heat-treated Mongshu Rubies
Mongshu rubies are characterized by a central blue-to-violet core in intense red crystals, healing feathers, several distinct growth zoning patterns and very fine white needles on inclusions in untreated stones (Peretti et al. 1995). Transparent calcite inclusions and dense silk zones occur less commonly than in Mogok rubies. B�hmite occurs occasionally along twin planes.
Nearly all Mongshu material is heat-treated to remove the bluish or violet tint and thereby improve the body color. Local treatments (in Myanmar) involve temperatures from 700 to 1200 �C, probably without flux, that is inadequate to produce flux-glass feathers in cracks. Inadequate treatment may leave zones of blue intact. Wispy, veil-like fluid-inclusion feathers or "fingerprints", exsolved rutile needles and fine particles resembling snowflakes are diagnostic features in the treated stones. Comet-shaped silk stringers, as observed in Kashan synthetic rubies, have been detected in treated Mongshu rubies. Exsolved rutile grains and whitish healing feathers produce a hazy or "sleepy" appearance in cut stones. Inclusions surround by discoid stress feathers and inclusions that are whitish or bubble-like with high-relief rims are common in heat treated stones.
Mongshu-1: Stress fracture "feather" (upper left) and a healed fracture decorated with trains of irregular fluid inclusions ("fingerprint") are typical of heat-treated Mongshu stones. These Myanmar treated stones lack the glassy features of the high-temperature Thai-treated equivalents. [Frame is 3 mm wide.]
Mongshu-2: A single, healed stress fracture decorated with trains of irregular fluid inclusions, typical of treated Mongshu stones. [Frame is 3 mm wide.]
References:
- Hughes, R.W. (1997) Burma (Myanmar) 300-343. In Ruby & Sapphire. RWH Publishing, Boulder, CO. pp. 511.
- Kammerling, R.C., and Scarratt, K. (1994) Myanmar and its gems—An update. Journal of Gemmology 24, 3-40.
- Peretti, A., Schmetzer, K., Bernhardt, H.-J., and Mouawad, F. (1995) Rubies from Mong Hsu. Gems and Gemology 31, 2-26.
- Sanchez, J.L., Osipowicz, T., Tang, S.M., Tay, T.S., and Win, T.T. (1997) Micro-PIXE analysis of trace-element concentrations of natural rubies from different locations in Myanmar. Nuclear Instruments and Methods in Physics, B 130, 682-686.
- Smith, C.P., and Surdez, N. (1994) The Mong Hsu ruby: a new type of Burmese ruby. JewelSiam 4, 82-98.
| Mogok | Nawarat (Pyinlon) | Nayaseik (Kachin) | Sagyin | Mongshu (treated) | |
| Color: | pinkish to intense deep red | medium red w/ purplish overtone | pinkish, rarely intense red | pinkish to medium red | medium to intense deep red (blue may remain after inadequate treatment) |
| Fluorescence (in daylight) | strong to very strong | strong | strong | strong | |
| Zoning: | bands and swirls | swirls | pronounced bands | ||
| Inclusions: | |||||
| Calcite | common w/ twinning or cleavage | subhedral to rounded | subhedral to rounded | subhedral to rounded | subhedral to rounded but heating destroys |
| Dolomite | often yellowish | yes | yes | ||
| Apatite | prisms | yes | yes | ||
| Titanite | yes | ||||
| Spinel | yes | probably | |||
| Rutile | yes, well-formed | yes | very small | ||
| Mica | muscovite | biotite | yes | ||
| Feldspar | yes | yes | |||
| Pyrite/ Pyrrhotite | yes | probably | yes | ||
| Others | many | white unknown | |||
| Rutile Silk: | characteristic; patchy to uniform | thin, patchy, and in bands | thin and patchy | rare | comet-like wisps |
| Clarity: | fluorescent to silky haze common | transparent but included | transparent w/ patchy haze | ||
| Healing Feathers | Common, w/ tiny fluid inclusions | "Fingerprints" are characteristic |
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