Wednesday, September 17, 2008

What makes natural alexandrite so expensive?

Supply and demand affects gemstone prices more than any other factor. Alexandrite is so expensive because it so rare and production has always been limited. Its historical association with the last of the Russian Tsars has created interest and allure. Everybody with an interest in gemstones seems to know something about alexandrite's unique history and the story has added to the stone's mystique. With a hardness of 8.5, alexandrite is an ideal gemstone, not only rare and beautiful but also hard and tough so it can be used in any kind of jewelry.

Example from - bluish green in daylight and purple red under incandescent light, the color change is exceptionally strong and attractive. The change is apparent without even changing the lights.

Alexandrites this large are extremely rare and this is a special stone. Although the clarity is not that good, this is a stone with character.

An antique setting might be the best way to set this stone. The cutting and proportions are good and the price is right. $3000 /ct. is a steal for an alexandrite this large!

Monday, August 11, 2008

What IsThe Alexandrite Effect?

The term alexandrite effect refers to the apparent change of color in certain minerals from blue-green or greenish violet in daylight to red or reddish violet in incandescent light. It has been determined that the absorption spectrum of all alexandrite-like minerals is characterised by transmission maxima in the blue-green and red regions and by a transmission minimum in the yellow region. The color of minerals with two such regions of transmission is determined in daylight (richer in blue and green) by the position of the transmission maxima and in incandescent light (richer in red) by the ratio of transmission in the red and transmission in the blue-violet sections of the visible spectrum.

The origin of this color change is often attributed to dichroism, but simple observation shows that the change depends chiefly on the nature of the incident light. In antiquity this change was from sunlight to candlelight and this exhibition is still used today by many gemologists and jewelers. Careful study of the color changes in chromium compounds by means of tristimulus analysis proves that the color change is due to the response of the human eye and brain and not to any unexpected changes in the properties of the stone.

As the chromium composition moves from those values which yield green compounds to those values which yield pink compounds, the interband minimum in the spectrum moves from near 525mp toward shorter wavelengths. The human eye is very sensitive to green light and is less sensitive to red and blue so it responds most strongly to the green light and the compound appears green. As the light passed by the interband minimum becomes more blue and the light passed by the long wavelength minimum becomes brighter red, the eye shifts its response from predominantly the green stimulus to a mainly red stimulus with some blue component. The gemstone now appears reddish.

Monday, March 17, 2008

Where can I test and appraise my alexandrite?

The most well known gemological laboratories are listed below and all of them are equipped to test alexandrite.

Many jewelry stores provide appraisal services for insurance purposes so try to contact a local gemologist for appraisals.

Sunday, February 17, 2008

Prophetic Russian Gemstone

Alexandrite became symbolic of the reign of Alexander II, and later tsarist Russia in general. The fact that the stone colors of red and green echoed the principal colors of Imperial Russia endeared it to many. Moreover, the magic of the changing colors directly reflected the thoughts of a society ruled by Tsars since 1480, where every written and spoken word had a second meaning and allegory was the main form of expressing notions different from the official ideology.

The mystical dualism of Alexandrite lies within Tsar Alexander II's figure who ascended the throne during Russia's defeat in the Crimean War of 1855. The early part of his reign was characterised by sweeping reforms and his liberal approach earned him the title of "Tsar Liberator".

The green of Alexandrite in daylight was taken to represent the hope and revival brought to Russia by Alexander II's efforts. "Green morning full of hopes" came into the lives of many when Alexander II emancipated the serfs and initiated the transformation of the flagging agrarian Russian economy into an industrial state.

Alexandrite is the stone of duality. Green or red, good luck or misfortune, the significance is interpretive and related to the social and historical context of the time and the culture. Forever changing its colors, alexandrite is a magical gemstone with universal appeal that continues to fascinate and be admired by astrologers, scientists, and gem lovers throughout the world.

Melt techniques used to produce synthetic alexandrite

Today the Czochralski pulled-growth method is used to make synthetic alexandrite.

The ingredient powders are melted in a platinum, iridium, graphite, or ceramic crucible. A seed crystal is attached to one end of a rotating rod and the rod is lowered into the crucible until the seed just touches the melt. The rod is then slowly withdrawn. The crystal grows as the seed pulls materials from the melt, and the material cools and solidifies.

Owing to the surface tension of the melt, the crystal stays in contact with the molten material and continues to grow until the melt is depleted. Crystals formed with this method can be very large, -- more than 50 millimetres in diameter and one metre in length with a high degree of purity.

Although Czochralski pulled boules are much more expensive than flame fusion boules to produce, their cost is still a fraction of the natural materials that they imitate.