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SRI LANKAN GEMS IN PICTURES

Sapphires for Royalty

 

Gem Mine - Sri Lanka

 

River Bed Mining

 

Mechanized Mining

 

Collecting Gem Earth

 

Washing Gem Earth

 

Picking the Gems

 

Rough Sapphires

 

Traditional Gem Cutting Maching

 

Chrysoberyl Cat's Eye

 

Fine Yellow Sapphire

 

Treatments to Ruby & Sapphire

 

TREATMENTS TO RUBY & SAPPHIRE

 

If you have eaten meat, fruit and milk products bought from a supermarket, you have consumed food which has been irradiated, dyed, heat treated (Pasteurized), coated with wax, injected with hormones and sprayed with dangerous chemicals. The food industry uses these treatment methods because most people prefer to buy appetizing, shiny, good size, bacteria-free food products.

Untreated food however, is available and some people are willing to pay higher prices for it. The organic produce often looks scrawny and dull, yet it's priced high. Vendors may point out the holes in the vegetables as an indication that no pesticides were used on them.

If the supply of gems were limited to those specimens that are naturally attractive, they'd be so expensive that most of us could never own them. Therefore, it's not surprising that the gem industry uses many of the same methods as the food industry to enhance the appearance of gems.

The heat treatment of corundum has become so common that all rubies and Sapphires are assumed to be treated unless otherwise indicated. Untreated stones are rare, and sell at a premium.

 

HEAT TREATMENT

 

 

For centuries, Rubies & Sapphires have been heated to improved their color and clarity. However, in the past 20 years, heat treatment has been done on a wider scale and at much high temperatures - 1700C and above.

When corundum is heated at temperatures above 1700C the silk (fine hair like needles inclusions)is dissolved and produces color, thereby improving color and clarity.This high temperature heat treatment can turn silky off-white or near colorless Sapphires clear blue. Rubies having silk appear less brownish or purplish and improve their clarity when you heat corundum below 1600C and above 1200C, you can create or improve star corundumby causing silk to crystallize. Thus the heat treating process can go in two directions to improve thee silk and lighten the color.

Heat treating is widely accepted because it causes a permanent improvement of the entire stone.Nevertheless, high quality heat-treated stones are often valued less than their untreated counterparts.

Untreated rubies and sapphires are rare, and rarity is prized in the Jewelry trade.It doesn't matter whether a stone was heated or not. The overall quality determines the prices.

To detect heat treatment is rubies and sapphires, gemologists usually must examine them under magnification. Heated stones may have fuzzy color areas and bands, surface pock marks, melted facets. Dot-like rutile needles or glassy circular cracks around natural crystal inclusions. Fluorescent reactions to ultraviolet are also studied. Heat-treated Blue Sapphire, often turns a faint chalky green under short-wave U.V. light.

 

SURFACE DIFFUSION

 

 

This treatment is usually done to make pale of colorless Sapphire without silk look blue. It may also be used to turn stones red, orange or yellow or to form a star. The pale stones are packed in chemical powders and then heated to 1700C and above until a thin layer of color covers their surface. Diffusion is relatively new (about 25 years old, according to patent records) and is not very well accepted by the trade. The color is permanent, but is only on the surface of the Stone. Consequently,the color can be polished or cut off leaving the grey or colorless interior exposed. It is important to deal with reliable sources and have major purchases checked by an independent gem laboratory.

 

IRRADIATION

 

 

Colorless sapphires are irradiated to make them improve color. Pink Sapphires may be irradiated to turn them to Padparaschas. Irradiation also occurs naturally. Some gems have been colored by natural radioactivity in the earth's crust.

 

OILING AND DYEING

 

 

Low quality rubies and sapphires (particularly cabochons and Indian star rubies and beads) are often dyed with a colored oil to hide cracks and improve color. To be oiled stones must have surface fractures which allow the oil to penetrate. Dyed corundum is generally not accepted in the trade. Dye treatments provide a practical means of making low-grade corundum look better. People who otherwise could not afford a natural ruby are able to buy one that looks acceptable.

 

SURFACE AND FRACTURE FILLING

 

 

It is not uncommon for rubies and sapphires to have pits or cavities, especially on its pavilion (bottom). Around 1984, rubies with glass-filled cavities began to be repaired. Since it was fairly easy to detect the types of filled stones, they were rejected by the world market and most have disappeared.

Since that time a new kind of filled ruby, which is much harder to detect such as borax as a result a glassy molten material is deposited in cavities and surface-reaching cracks. The glass infilling is relatively permanent and irreversible and it improves a stones durability since the fractures are healed shut.

Most of the in filled corundum on the markets today is ruby from the "Mong Hsu" depost is Myanmar (Burma), which was discovered around 1990. Unfortunately Mong Hsu rubies typically have numerous minute fractures. Very dense. "Silk" cloud and a strong purplish color which make most of them look like low grade cloudy rhodolite garnet - ordinary heat treatment turns the stones into attractive red color. Since "Mong Hsu" stones are heavily fractured they must be heated in borax flax to prevent cracking and to improve their clarity.

 

BERYLLIUM DIFFUSION

 

 

This is a new process in Thailand that involves the diffusion of beryllium into ruby and Sapphire at very high temperatures in an oxidizing atmosphere. It was first discovered in 2002.Beryllium diffusion can penetrate deep, sometimes coloring the entire stone. The colors produced by this process are mainly yellow, orange, yellowish orange, orange pink and orange red. Some types of dark Blue Sapphires can be lightened using beryllium-diffusion process and virtually any color of ruby and sapphire can be reproduced by this process.

 

Beryl

 

 

Emerald belongs to the mineral species called beryl, which is a precious gemstone. In Sanskrit emerald is called Marketh and also Tarkshya. It is however, from its Persian name, Zamurrad, which traveled to Greek as Smaralds, then through Roman to Latin, as Esurde, and finally took shape as Emerald in the 16th century.

The emerald was called Neronianus, after the Roman emperor Nero using an eyeglass made of it for watching the feats of gladiators. Cleopatra's magnificent jewels included a profusion of emeralds from her own mines,Napoleon III was reputed to have presented Empress Eugenie an emerald 'Clover Leaf' sparkling with diamond dewdrops. Soon after her marriage, the city of Paris presented her with 2 wonderful diadems of emeralds as a wedding gift.

One of the finest emeralds known was said to be one of 136 carats, which used to belong to the Czars of Russia and is now among the Soviet treasures. However an emerald statute which was found in a tiny shop in a back street of Amritsar in August 1960 has made the Russian emerald seem small by comparison.

The Duke of Devon shire in England has an enormous crystal, which is a two inch cube with flaws and inclusions in the texyure.Purity, Weight, coolness, freedom from dust and beauty are the five principal qualities of emeralds, s according to the ancient belief "cleanse men from all sins"

Some of the world's finest emeralds come from the famous Mazo mines in Colombia. The Colombian emeralds are known here by the name of "Box Emeralds"they are compact and display fine color and water.

Egyptian emeralds are pale and often cloudy. Emeralds of Brazil are yellowish. Zimbabwe's Emeralds are in dark hue and black spots in its composition as other African Emeralds. All types of Emeralds are produced in the Urel Mountains they are less attractive.Emeralds are also produced in India,Pakistan,Norway, Australia, South Africa , Mozambique and Madagascar.

Emerald belongs to the hexagonal system of crystallization, as it comes under the species of Beryl. And is one of the lighter variety of transparent gem materials, its specific gravity is from 2.67 - 2.75, It is nearly double the size of a sapphire of equal weight. Chemical composition is Be3AL2Ai6O18 with Chromium (Cr+3) and thehardness of emerald is 7.5 - 8. It is transparent and its Iustre is vitreous. It possesses double refraction, though in very small degree, and acquires positive electricity by friction. There is another variety of Beryl also in green color due to vanadium. It is not called emerald, it is known as Green vanadium Beryl, and some of very fine green beryls due to nvanadium have been discovered. But to designate green beryl as emerald, it should show absorption lines in red in the spectrum.

 

Other Varieties Of Beryl

 

 

Chromium - The King Maker

Can we talk abut precious gems without reference to ruby, emerald oralexandrite?all of them have two things in common ; they are beautiful and hance valuable and each has a fraction of chromium (Cr) in them. Cr produces the purest red in ruby and red spinel, the most baeutiful green in emeraldand a wonderful change of colour in alexandrite; green in day light and red in candle light or incandescent light.

Not only those, many other gem varieties get their beautiful green whaen a bit of cr is present in them, and most often refer to them with a prefix 'chrom'; chrom diopside, chrom tourmaline etc. Even without cr they are green but not the best green.

So would it not be interesting to know a little about chromium and appreciate its role as "king maker". Most Gemstones get their colour due to the presenceof transition elements in them: v, Cr, Mn. Fe, Mn, Fe Co, Ni, Cu.

In general ,electrons in atoms occupy certain orbital shells around the nucleus , like planets around the sun. Each shell represents an energy level. the innermost shell can contain 2 electrons, next shell upto 8, next upto 18 etc. The inner shells are full and generally outer shell contain a fewer electrons than it can accommodate. But this is diffferent in transition elements, inner shells may not contain full quota of electron (see figure 1-Cr). Cr can have upto 18 in third shell but it has only 12.

Electrons in most elements exist in these shells as pairs spinning in oppaosite directions. However in transition elements, in the incomplete shells many electrons will remain unpaired. When white light (dey light) falls on a gamstone, part of it is absorbed by the electrons and jump in to higher energy levels and the unabsorbad component of light reach us as the colour of the gemstone.

Remember light is a from of energy and white light consistsof different coloured waves as you see in the rainbow, each wave having a different colour and having a different colour and different amounts of energy. The amount of energy required by a paired electron is higher than that required by an unpaired electron. Therefore it is the unpaired electrons of transition elementswhich absord part of light and cause colours in them. Most of gems get their colour due to transition elements but there are some which do not have transition elements but their colouring mechanism is different.

Now let us look at the role of the chromium gems. It can exist as a an impurity or as a part of the chemical formula. in ruby, emerald and alexandrite, Crexists as a substitute atom for aluminium atom.. Cr atom has six unpaired electrons, three involving bonding with other elements in the atomic structure and the other three changing energy levels by absording energy from white light.

Three of the unpaired electrons in Cr can occupy in different orbits or energy levels. The amount of energy required to raise an electron from ground level A to C is about 2.25 electron-Volts or eV which corresponds to yellow-green light and hence some electrons absorb yellow-green range of light(See figure2).

The amount of energy required to raise electrons from A to D leve is 3 eV and it Corresponde to violet part of visible light . So some electrons absorb violet colour. Millions of electrons in the gemstone absorb yellow-green and violet colours, so that stone appears in red.

 

 

Emerald ( Be3 Ai2 Si6 O18 +Cr)

 

The force thet surrounds cr (which has replaced Aluminium) is weaker than that of ruby. Therefore the energy levele of electrons are different. in this case about 2eV of energy, it is red part of light that is absorbed and the residual colour is the most beautiful pure green.

 

Alexandrite ( BeAi2 O4+Cr)

 

The forces that surrounds Cr is intermediate in Strength as compared with ruby and emerald. Therefore the C level is between 2 eV and 2.25 eV. The slight variations in the absorption can cause different colours. In day light high energy blue-violet components of light is higher and therefore the stone is green in daylight. The candle light or tungsten light is rich in yellow red component and hence stone appear in red in that light.

In general , electrons in atoms occupy certain orbital shells around the nucleus,like planets around the sun. Each shell represents an energy level. The innermost shell can contain 2 electrons, next shell upto 8, next upto 18 etc. The inner shells are full and generally outer shell contain a fewer electrons than it can accommodate. But this is different in transition elements in transition elements,Inner shells may not contain full quota of electron (see figure 1-cr).Cr can have upto 18 in third shell but it has only 12.

 

Polyasterism - the hottest star

Polyasterism is the display of more than one star within a narrow angle of observation; they aren't stars of same star-¬network. Although quartz and many other species display polyasterism the study emphasized the phenomenon in star sapphire concerning its high commercial potential.

About 0.1% of Sri Lankan star sapphire produce and greater percentage of fashioned stones display multiple stars or polyasterism. Relatively common two-stars are often called "Siamese twins" and rare three-stars "triplets" in the trade.They not only comprise 6-ray stars but rarely 12-ray stars too, and prevalent among blue star, star ruby, and all other sapphire colors, sometimes fetching higher prices than that of single star stones.

Apart from usual criteria. symmetry, of component stars dominates the valuation of polyasteric stones. Morphological disturbances in the single crystal or forming a compound crystal by bonding/fusing/cementing several crys¬tals togetherby geological reasons or Branching/penetrating of crystalsare the two main causes that convert a star sapphire into a polyasteric stone.

Morphological disturbances include - basal, prismatic and rhombohedral - glides, and are favored in the same precedence order if one type is restricted by local stress. strain or other reason.

Relative displacement of two or more sections by glide causes display of asterism independently in the individual sections arising from their rutile needle inclusions - this is the polyasterism in single crystals. Similarly compound crystal formed by aggregation of crystals display the effect.

Figure 7 shows relative displacement of two sections of kornerupine crystal by glide, which cuts the cat's-eye in half and shifts fire two halves by equal distance.Basal, prismatic and rhombohedral - glides takes place similarly in the sap¬phire stones.Figures-5, displays clockwise- polyasterism by basal glide (0001) [1120],prismatic glide (1120) [1010], rhombohedral glide (1011) [1120], and a photograph of a polyasteric sapphire caused by basal glide showing two stars.

Figure 5.

 

Figure 6. Ways of forming a compound crystal of a polyasteric sapphire.(a) Three wire frame diagrams of sapphire crystal branching at the terminations displayed along with stones to be fashioned.(b) Polyasteric stone probably fashioned from a compound crystal shows group of rutile cores at the centre that have revolved by 30o from the background core yielding polyasterism. (c) Interpenetration from a side. (d) Bonding/ fusing/ cementing of two crystals together.

 

 

New Discovery of Aquamarine in Sri Lanka

Except for Moonstone which are mined from a weathered pegmatite in Meetiyagoda and in-situ Chrysoberyl in Pattara no other commercially viable gem deposit has been known to exist in Sri Lanka.

The recent accidental discovery of Aquamarine were found during mining for vein quartz (for industrial silica quartz)in the Akkerella estate belonging to Kahawatta Plantations Ltd. Which is located about 25 KM south east of Ratnapura.

Fig 1 : shows the distribution of Vein quartz at Akkarella Estate, Opanayake.Previous occurrences of Auqamarine in Sri Lankahad mostly been from Ratnapura & Nawalapitiya & these stones were always water worn. The recent findings have generated a geological interestin relation to the genesis of gemstones in Sri Lanka.

This vein quartz field stretches about 2 kilometers in length. The Aquamarine is found in association with phlogopite mica and schorl (black tourmaline) is evidence of the pneumalytic genesis of this pegmatite. The size of the crystals vary but samples of upto 10cm or more have been found.The color varies from a pale sky blueto a darker blue resembling the color of Santa Maria Aquamarine. Tests as to the nature of the fluid inclusions ib the stone asn research into the details of the chemistry of the stones are currently, being carried out.

A few samples of Aquamarine had been investigated for their gemmological properties. They are listes below.

The nearby estate of Hunuwala, which is about 6km north west of Akkarella,shows evidence of the continuation of this pegmatite mineralization. The National Gem and Jewelry Authority has recently auctioned off the Hunuwala estate for gem mining.Larger crystals of colorless Topaz have been found there; some even measuring up to about 10 kilograms.

With a history in gem mining that goes back some 2,500 years, Sri Lanka has been known through the centuries as "Rathnadeepa", or the "island of gems". Stonesmined on the island include alexandrite, alexandrite cat's eye, amethyst, aquamarine, beryl, chrysoberyl, chrysoberyl cat's eye, citrine, garnet (almandine, hessonite,pyrope, rhodolite, and spessartite), moonstone, ruby, star ruby, sapphire (blue, golden, orange, papardscha, pink, white, and yellow), star sapphire, spinel, tourmaline, topaz, and zircon.

In modern Sri Lanka, gemstones are a national resource that belong to the state.Mining is controlled by the National Gem and Jewellery Authority (NGJA),which has in place an intricate mining license system that makes it possible to mine on private as well as on public land, with the latter being managed mostly through a tender system.

Seeing that Sri Lanka's gemstone exports approach $25 million a year, it is surprising that the vast majority of its mines are small, very labor intensive operations that use minimal mechanization. This, the NGJA argues, is not necessarily a negative thing, since the gem mining sector creates employment opportunities for several hundred thousand people, including in support industries such as timber, water pumps,washing baskets and other tools, and transportation, etc.Furthermore, the government has not encouraged large-scale miningin order to minimize damage to the environment. With these policies in place, NGJA expects that the known mining reserves will last for another 100 years.

Ratnapura is the center of the sapphire mining industry, with at any one time between 30 and 50 licensed pit mining operations active in the area. Each operation typically involves five to 50 miners. Heat treatments are mostly done in Ratnapura and Colombo.Reportedly, around 700 to 1,000 modern furnaces are now in operation on the island.

Aquamarine in Sri Lanka was usually found in Ratnapura and Nawalapitiya, and the stones were always waterworn.However, a recent accidental discovery of aquamarine crystals led to a sudden gem rush. These stones were found during mining for vein quartz (silica quartz) in the Akkerella estate, about 25 kilometers southeast of Ratnapura, which belongs to Kahawatta Plantation Ltd.This aquamarine is found in association with phlogopite mica and schorl (black tourmaline). The size of the aquamarine crystalsvaries up to 10 centimeters or more. The color varies from light sky blue to darker blue resembling the color of Santa Maria aquamarine. Research is now underway into the fluid inclusions and details of the chemistry of these aquamarines.

A continuation of the pegmatite mineralization is foundat the nearby Hunuwala estate, northwest of Akkerella.The NGJA recently auctioned the rights to gem mining at Hunuwala,which has produced larger crystals of colorless topaz, some even up to about 10 kilograms

 

 

2006 ICA Mining Report Sri Lanka

Moonstone comes from the famous moonstone mines in Meetiyagoda, in the south of the island, near Galle. There, the devastation caused by the December 2004 tsunami is still very visible, but the moonstone mines are location a few kilometersinland and did not suffer.The production here, which began more than 50 years ago,is currently very low. Only two mines are active. The large high-quality material with strong blue color and shine is now a memory only, as the layers producing these stones have been depleted.

Currently, a deeper layer producing smaller moonstones with a more silvery hue is being mined. Moonstone is also being mined near Dumbara, close to Kandy.This mine has been producing for more than 100 years and has yielded some very fine-quality gems. The best stones ever roduced in Sri Lanka reportedly came from this area.

Chrysoberyl is supposedly mined in Pattara, but no other commerciallyviable deposit of this gem has yet been found in Sri Lanka.In the Elahera area, some mechanized mining is reported, but in general, openpit mining remains the rule.

During seasons when agricultural activities do not require all the local labor force, 200 to a few thousand locals dig for stones in their backyards, which are mostly rice paddy fields, or in the surrounding jungle. In Elahera, unlike in Ratnapura, many women are involved in mining.The quantity of gemstones produced there, despite the number of miners involved, does not appear to be high.