Ruby is the red variety of corundum with hardness of 9 on Moh’s scale. Among the natural gems only moissanite and diamond are harder. The red color of ruby is caused mainly by the presence of the element chromium, which is also the cause of fluorescence in ruby, intensifying the body color. The very best color in ruby is sometimes described as “pigeon’s blood”. Its name comes from ruber, Latin for red. In the ancient language of Sanskirt, ruby is called ratnaraj, or “ king of precious stones”. For many cultures, rubies signify romance, wealth and success. Ruby is the traditional birthstone for July. Ruby is one of the most historically significant colored stones and is considered as one of the finest stones for jewelry settings.

Ruby may be available in various shades of red such as pure red, or additional orange to purple modifying colors to the red. The most valuable ruby colors are red to slightly purplish red with medium to medium-dark tons and vivid saturations. Burmese Ruby is the most famous and sought after around the earth, but fine-looking crystals have been originated elsewhere. Some of them were mines in places such as Afghanistan and Vietnam. These fine rubies form in marble hosted rocks and fluoresce under ultra violet light. Rubies are expected to have at least some inclusions. These inclusions are rutile needles (silk), included crystals; fingerprint inclusions and etc. some inclusions actually contribute positively to a gem’s appearance. For example the presence of rutile silk causes light to scatter across facets that might otherwise be too dark, adding softness to the color and spreading the color more evenly throughout the stone. Some Afghan rubies display these characteristics the same as rubies from Myanmar. Inclusion free rubies are almost none existent. Today almost all rubies are heat-treated and untreated rubies command a higher price in the trade. Heat-treatment is most common treatment for ruby and it is used to improve color and clarity. However other treatments exist such as: fracture filling, cavity filling, quench crackling, dying and lattice diffusion. At Himalayan Gems and Jewelry most of our stock is untreated ruby sourced from Jagdelak mine high up in the Himalayas, in Afghanistan. The ruby deposits of Afghanistan have been famous for centuries, and Jagdelak is the most important deposit of the country. Jagdelak rubies are historically important and rubies form this mine are scarce, but they can exhibit the coveted “pigeon’s blood” color. We also offer some heat-treated rubies and the treatment is always disclosed.

Characteristics of Afghanistan ruby (Jagdalek)

Nothing exists in the literature regarding the gemological characteristics of rubies or spinels from Badakhshan, primarily because no twentieth-century eyewitness accounts exist of the mines. In addition, gemological descriptions of the important specimens of history, such as the Timur ruby and the Black Prince's ruby, have never been published.

The situation at Jagdalek is somewhat better. Material has filtered out throughout the 1980s. In the early part of that decade, the author acquired a number of faceted and rough specimens from Jagdalek. The following is based on his first-hand studies, supplemented by those of Bowersox (1985), Barthoux (1933), Beesley (1986), Brückl (1937) and Themelis (1988).

Occurrence

Afzali (1981) has reported the Jagdalek mine to lie in Kabul province at 34° 26' N, 69° 49' E. For those who read German, the most complete description of the mine is that of Brückl (1937). The rubies are said to occur embedded in a regionally-metamorphosed marble cut by granitic intrusions of Oligocene age.

Table 1: Properties of Jagdalek (Afghanistan) ruby

Property	Description
Color range/ phenomena	• Near colorless to a deep red, often slightly purplish, strongly fluorescent. Violet stones are seen on occasion.
Geologic  formation	• Ruby is found embedded in a regionally metamorphosed marble cut by granitic intrusions of Oligocene age.
Crystal habit	• Most crystals are hexagonal prisms (short or long) with development of rhombohedron and pinacoid faces. Spindle-shaped bipyramids are also sometimes seen.
RI &  birefringence	n [epsilon] = 1.762; n [omega] = 1.770      Bire. = 0.008
Specific Gravity	~4.00
Spectra	Visible region • Strong Cr spectrum (similar to rubies from other localities).
Fluorescence	UV • Strong red to red-orange fluorescence (LW stronger than SW).
Other features	May be dyed or heat treated.
Inclusion types	Description
Solids	• Calcite; rhombs • Phlogopite mica; books • Rutile; prisms and knee-shaped twins • Garnet • Chondrodite • Apatite • Pyrite • Spinel • Graphite • Hornblende • Dolomite
Cavities (liquids/gases/ solids)	• Primary negative crystals. • Secondary healed fractures are common. They occur in a variety of patterns and thicknesses. • Iron oxide stains are common in cracks (these may be removed during heat treatment).
Growth zoning	• Straight, angular growth zoning parallel to the faces along which it formed; irregular 'treacle'-like swirls in other directions. Distinctive are the blue color zones intermingled in most stones, similar to Vietnamese rubies. Growth zoning is extremely sharp and prominent.
Twin development	• Growth twins of unknown orientation. • Polysynthetic glide twinning on the rhombohedron.
Exsolved solids	• Dense zoned clouds of (often, but not always) tiny particles (probably rutile), parallel to the hexagonal prism (3 directions at 60/120°) in the basal plane. • Boehmite, long white needles along intersecting rhombohedral twin planes (3 directions, 2 in one plane, at 86.1 and 93.9°).

Color range

Rubies from Jagdalek are only rarely encountered in faceting quality, but when clean can be magnificent. In terms of color, Jagdalek rubies resemble most the gems of Vietnam, Burma and Sri Lanka, being strongly fluorescent and often of a slightly pinkish or raspberry-red hue similar to rubellite tourmaline. A small percentage are of violet hue.

Solid inclusions

Various types have been found in Afghan rubies. Common are colorless blocks displaying rhombohedral cleavage, most likely of calcite. Inclusions of calcite are not surprising, considering the fact that Jagdalek rubies are found in a marble matrix, just as in Burma. Transparent plates and books of hexagonal outline are also seen. Due to their anisotropic character between crossed polars and prominent basal cleavage, they are most likely mica. Other platelike inclusions consist of irregular distorted shingles which are opaque and black or slightly gold in color. These also display a somewhat micaceous appearance. Additional solid inclusions seen were rounded colorless grains of low relief and, in one specimen, corroded blocks of a yellow color. Several specimens examined by the author contained deep red-orange prisms of square outline and submetallic luster. Some were knee-shaped twins with obvious reentrant angles, indicating rutile.