October Birthstone-Opal or Tourmaline

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Tourmaline

Tourmaline is the October birthstone, and those born in October are indeed very lucky, as they have a beautiful array of colors representing all the colors of the rainbow and their different shades and combinations, to choose from. Some of these colors and combinations are:-red, orange red, reddish orange, orange, yellow, greenish yellow, yellowish green, green, bluish green, greenish blue, blue, reddish purple, purplish red, pink, brown, black, and colorless

The original source of tourmaline was Sri Lanka (Ceylon), a small island at the southern tip of the Indian Sub-Continent. Almost 90% of the Sri Lankan soil is gem bearing, and mining had been taking place for thousands of years. Historical evidence suggests that precious and semi-precious stones had been exported from Sri Lanka to King Solomon's Kingdom, and some of these stones may have adorned the crown of Queen Sheba. Likewise Royal Families around the world and particularly the British Royal Family had acquired rare and expensive precious and semi-precious stones from Sri Lanka since ancient times.

The two main local languages spoken in Sri Lanka are Sinhala and Tamil. The name Tourmaline is derived from the Sinhala word "Tora malli", meaning mixed stones or assorted stones of different colors. The term probably was coined by the early Moor traders, who were the descendants of the  early Arab settlers, who settled in the country between the 5th and 8th century A.D. and who are considered to be pioneers of the gem trade in Sri Lanka. Most modern Gemmologists are genuinely puzzled by the abilities believed to have been possessed by these ancient Moor traders, who were able to identify accurately both in the rough and cut and polished state, any one of the variety of gem stones found in Sri Lanka, such as Sapphires, Rubies, Garnets, Tourmalines, Amethysts, Aquamarine, Moonstone, Spinel, Topaz etc. These identifications were made without the aid of instruments that are presently at the disposal of the modern Gemmologists, for measuring specific gravities, optical properties, hardness etc.


Tourmalines were considered as semi-precious stones since ancient times and therefore less valuable, but recently it has become a favourite gem stone in the gem and jewelry trade. This may be because of the wide variety of colors in which the stone is available, and it's good hardness of 7.0 to 7.5 on the Mohr's scale. Tourmalines also have healing and other Metaphysical properties thought to be derived from the electromagnetic nature of the mineral. This coupled with it's demand as a birthstone for October, has pushed the prizes of all types of Tourmalines to a level equal to that of precious stones.

Tourmalines have been used since ancient times by the Aborigines, certain tribes in Africa, and the native Americans, as a medicinal stone to relieve asthma, to cure Psychiatric disorders like fears, anxiety, obsession, and neurosis. The metaphysical properties of tourmaline include strengthening of body and mind, protection from negative influences, helping in seeking inspiration, protection against unwanted energies, and evil forces, protection against dangers and misfortune.

Tourmalines are complex Aluminium Borosilicates with a changing composition. Many different elements can be accommodated in the crystal lattice and this accounts for all the different colors in which tourmalines are found in nature. Some of the elements that can be found in the Crystal lattice are Lithium (Li), Sodium (Na), Calcium (Ca), Iron 2(Fe++), Iron3 (Fe+++), Magnesium (Mg), Manganese (Mn), Chromium (Cr), Copper (Cu), Vanadium (V).

Tourmalines are classified according to their colors, but these classes are sometimes assigned different names.
Red tourmaline - Rubellite
Blue Tourmaline - Indigolite
Green Tourmaline - Verdelite
Green Tourmaline - Chrome Tourmaline (green caused by Chromium)
Yellow Tourmaline - Canary Tourmaline
Brown Tourmaline - Dravites
Black Tourmaline - Schorl

Paraiba tourmaline with an intense blue to bluish green color was first discovered in 1987,in Paraiba State in Brazil. The blue color is caused by Copper (Cu), but a certain quantity of Manganese (Mn) may also be present. If the concentration of Copper is greater than that of Manganese, the blue turquoise and green color predominates. On the other hand a greater concentration of Manganese can cause violet, purple, and red hues. However the violet, purple, or reddish hues can be eliminated by appropriate heat treatment, leaving only a brilliant bluish or bluish green color. The color has a unique "fire" and therefore referred to as Neon Or Electric. The unique properties of Paraiba Tourmalines have made them one of the most sought after gemstones in the world.

In Brazil the Paraiba is almost exhausted, but new sources of Paraiba have been discovered in  South Western Nigeria. This is not surprising, because, before continental drift started, the South American Continent was attached to the African Continent. If on a map of the World, if the South American Continent is imagined to be shifted eastwards it fits exactly into the coastline of West Africa. Brazil and Nigeria come closer together in this imaginary exercise. Thus the Paraiba found in Brazil and Nigeria probably would have originated at the same time under the same conditions before the continental drift took place. Therefore the presence of Paraiba in Brazil and Nigeria provides strong evidence for continental drift that took place over millions of years.

Sometimes two or more colors can appear together separately in the same tourmaline. Such stones are referred to as bicolored and multicolored tourmalines. A special bicolored tourmaline is Water Melon Tourmaline, in which the outer layer of the crystal is green, and the inside is red, with black inclusions resembling seeds. Such stones are cut and polished flat across a crystal face to bring out all the features of the stone.

Tourmalines have two refractive indices-1.616 and 1.652.The difference 0.04 can cause some birefringence leading to doubling of back facets and inclusions. It has hardness of 7.0 to 7.5 on the Mohr's scale and a specific gravity of 3.0 to 3.3.

Tourmalines also have industrial applications such as use in high pressure gauges. The property of tourmaline becoming bipolar when subjected to high temperature and pressure is made use of in these applications.

Opal

Opal is the alternative October birthstone.

The name Opal may have been derived from the Sanskrit word "Upala", which means valuable stone. The Greek word "Opallios", meaning color change, could be another word from which the term would have originated.

Since ancient times opals were considered to be healing stones, with the power to heal depressive episodes. Opals were also believed to assist the wearers in their quest for real and true love.

In the past Opals were quite scarce, and the two main sources were Hungary and Czechoslovakia. But after the accidental discovery of large deposits of Opal in 1849, in the deserts of Australia, it has become a very popular and sought after gemstone. Today Australia is the world's largest supplier of fine Opals. Other smaller producers of Opal include the U.S. (Idaho and Nevada States), Brazil, and Mexico. Recently Opals have also been discovered in Ethiopia and Tanzania in East Africa and Mali in West Africa.

Opals occur in different varieties such as Dark or Black Opal, White or Light Opal, Milky Opal, Crystal Opal, Fire Opal etc. The important characteristic of all fine opals is their unique play of colors, caused by the dispersion of white light as it passes through the stone, splitting it into the different colors of the Spectrum. Opals that do not show the play of colors are called "Common Opals".

Opal has the same constitution as Quartz, made up of Silicon dioxide (SiO2),but the silicon dioxide is always associated with water. Thus Opals are considered to be Silica Gel, with varying percentage of water. Therefore Opals should not be exposed to heat for a long period, as loss of water can cause fissures in the stone and decrease it's play of color. It is advisable to wear Opal jewelry frequently instead of keeping them in storage, for this will help the gemstone receive water vapour from the air or the skin of the wearer.

the hardness of Opal is 5.5 to 6.5 on the Mohr"s scale. Thus Opal is a fairly soft stone, usually cut as cabochons, and prone to wear and tear. Therefore Opal jewelry should be handled with care, and now they are sealed with a colorless artificial resin to protect them.

In terms of value Black Opals are the most expensive followed by Crystal Opal, White Opal, and Milky Opal.

 

You are welcome to discuss this post/related topics with Dr Shihaan and other experts from around the world in our FORUMS (forums.internetstones.com)

 

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