Showing posts with label Red Sapphire. Show all posts
Showing posts with label Red Sapphire. Show all posts

Wednesday, May 13, 2009

Ruby, Rubies, Red Sapphire

Burma (Myanmar) is famous for producing the greatest amount of top quality ruby with a fine, clear, deep-red color. Most of the best quality ruby comes from the Mogok Valley in Burma and others from newer sources such as Mong Shu (discovered in the Shan State in 1991), and Namya, in the Kachin State, which experienced a rush in 2000. ?Pigeon blood? was once the paramount color for ruby but this appellation is now tricky as there is no standard behind it.

Ruby can be true red or red with some purple or orange overcast or going towards pink. On the last point, the fact is that ruby and pink sapphire are basically the same stone as they are both aluminum oxide with a small amount of chromium. High levels of chromium give red, lower concentrations give pink. There is no clear and worldwide-accepted borderline between what is a ruby vs. a pink sapphire. Rubies in Mogok and Mong Shu are found either in marble primary deposits in the mountains around the valley or in alluvial placers in the valley.

In Namya they are exclusively found in alluvial deposits in this swamp area. All Burmese rubies were born from a metamorphic process (as well as Vietnamese, Nepalese and Afghan stones). They are usually poor in iron, and as a result, show a strong red fluorescence which make them different from their cousins from basaltic deposits in Thailand or Africa. Rubies usually occur in Burma as tabular crystals with hexagonal prisms. Usually the basal plane shows markings consisting of striations, often as equilateral triangles, and prisms are commonly striated horizontally. Mogok also produces some more rare ruby crystals in which rhombohedrons are so well developed that the stone looks similar to a spinel crystal. For many centuries red spinels and rubies were associated with one another and believed to be the same stone.

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Sapphire, blue sapphire, red sapphire, Sapphire in matrix, Star sapphires

Blue is the most popular color for sapphire but sapphires can be found in nearly every imaginable color:

Sapphire is the gemstone trade name for the gemstones issue from the mineral corundum species with colors different than red. Red corundum is "ruby" Sapphire used alone means in fact "blue sapphire"

Fancy sapphires is the gem trade name for corundum with other color than blue or red. They can come in shades of purple, green, yellow, black, all colors except red, as "red sapphire" again is ruby.

Padparadsha sapphires are the most valuable of all fancy sapphires is their color is close to the color of a lotus flower. In fact, it should be a delicious mix of pink, orange and yellow. Padparadsha are typically coming from Sri Lanka, but natural padparadsha from Mogok in Burma are also known.

Royal blue is the typical color of Burmese sapphire from Mogok it is slightly violetish blue to true blue.

Cornflower blue is more velvety and typically from Kashmir (India), but is also found in Mogok, especially in the Thurein Thaung mine which is famous in Burma as several of its best stones were identified by some major laboratories as being of "Kashmir Origin".

Even after agreeing that origin is not a measure for quality when dealing with gems, the fact is that top quality Burmese sapphires, along with some Kashmir stones, are considered to be the finest quality for sapphire.

In the better qualities, determination of origin for these sapphires is a difficult task. Nowadays production from Mogok is scarce and production in Kashmir is very weak. Most of the sapphires currently in the market are coming from Madagascar and Sri Lanka but Thailand (Kanchanaburi), Cambodia (Pailin), Australia and China are also important producing areas.

Like ruby, many sapphires in the market nowadays owe their beautiful color to heat treatment, and some yellow stones get their color from irradiation.

Chanthaburi in Thailand is the world center for the heat treatment of gemstones which is something of a semi-scientific alchemy. This treatment ensures a steady supply of fine stones at affordable prices for gem-lovers the world over. In fact it has become such an industry standard that "unheated" rubies and sapphires are considered collectors items. They are still the gemstones of the very wealthy as they can attain really very high prices.

Sapphire can present many interesting particularities that make it one of the crystal and mineral collector favorite: their shapes cigars like or bi-pyramid are very attractive as sapphire comes in many colors. More rare but much appreciated are the hexagonal columnar crystals.

Sapphire in matrix can make very fine stones for displays, but such stones are rare and difficult to find in the market as most of sapphires are coming from alluvial deposits. These deposits can be from former metamorphic or basaltic weathered rocks. Most sapphires in Mogok were formed in feldspar (metamorphic origin) in the west of the Mogok valley near the Kabaing granitic dome. Some sapphires are also found sometimes in the north east of Mogok in strange iron rich matrix or also even stranger completely covered by spinel. Going further north near the Momeik city igneous sapphires are also found showing the incredible geologic complexity of the Mogok area.

Star sapphires are one of the gemstone collector favorite. Star in sapphire can result of 2 kinds of inclusions:
Rutile needles reflecting light as mirrors and that cross each other with 60 degrees angles are the reason of the moving 6 ray star effect.


Hematite platelets give the 6 rays stars in black star sapphire
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