Know About Gems
Superstitions and stories have been often surrounded to many gemstones. People believe that some stones made them richer or the other way it was the cause for their downfall. We, the gemmologists have no major role or knowledge in the astrology and therefore we do not want to discuss on the astrological aspects of gemstones at all.
Nevertheless, we can assure the general public the fact that there are various types of simulants (imitations) and also synthetic stones existing in the market, which can be mistaken for the Navagraha stones with which you wanted to try your luck. Beware of these synthetic and simulants.
In addition, there are colour enhancements being done to many gemstones by heat, irradiation, dye etc. This is again an important aspect one must be careful before buying the same.
It is, many a time, stated that the deeper the colour, the better the value of the stones especially for astrological purpose. If this is so, one has to be very careful, because today maximum of coloured stones, especially Ruby, Sapphire etc. seen in the market are subjected to some kind of treatments. In other words, the qualities of such stones are enhanced by various treatments.
We give below a brief description of all the Navagraha stones.
1. RubyRuby belongs to the noble Corundum family. The word Corundum is derived from the Sanskrit word “Kurand” or “Kuruvinda”.
Ruby name is derived from the Latin word “Ruber” (red), represents the embodiment of the most beautiful red colour conceivable in the universe. However the finest and most precious shade is the “Pigeon Blood Red”.
Ruby has been described by Dr. Edward Gubelin as the “Red Magic” and colour extract from a “drop of the heart’s blood of Mother Earth”.Ruby is considered to be the most powerful gems in the galaxy of gemstones; especially in the Indian context, amongst the Navgraha gemstones, Ruby occupies the center of the planetary position, representing the “Sun”.
Ruby is a power of love as you very rarely come across any other gem that can inspire such emotional vibrations as does the ruby. In short ruby has symbolised the highest earthly possession of love and power. Hardly any other gemstone can inspire such emotional vibrations as does the ruby.
Many red coloured stones which were not rubies were termed as ruby. The classic example is the Black Prince’s ruby in the Imperial State Crown kept in the Tower of London. It was tested in a gemmological laboratory and was identified as a spinel, a stone of much less value. Today such mistakes are not made thanks to the good testing instruments in gem testing laboratories. Besides spinel there are other red coloured gems which can be mistaken for ruby, they are tourmaline, pyrope garnet, red zircon, red beryl, synthetic rubies, synthetic spinels etc. The costliest amongst them is a ruby.
The best rubies come from Burma, now Myanmar. The Burma ruby is not only bright red in colour but has transparency and characteristic inclusions.
Today in the market one also comes across New Burma rubies that are heat treated and of much lower value. These are not very transparent, heavily included but of good red colour. Besides Burma, rubies are also found in Thailand, Sri Lanka, Mozambique, Tanzania, Kenya, Madagascar, Nepal and in India.
Good quality rubies having bright red colour, transparency, clarity and well proportioned style of cut can demand exorbitant prices. But one should also remember that it is possible to buy genuine rubies to suit one’s budget.
2. Yellow SapphireYellow sapphire is the stone that is said to represent the planet Jupiter (Guru, Pukhraaj). Surprisingly very few jewellers know that the yellow sapphire and the blue sapphire have the same chemical composition identical to that of ruby. All three have the same basic composition aluminium oxide and belong to the corundum family. The various colours are imparted due to certain impurities, the red colour in ruby is due to chromium, and the yellow colour is the result of iron whereas the blue colour in sapphire is caused by titanium as well as iron impurities.
Another important aspect which many people fail to understand is that there can be many yellow coloured stones of different mineral species. For example yellow beryl, yellow garnet, yellow chrysoberyl, yellow feldspar, yellow spodumene, yellow scapolite, yellow topaz all of which can look identical to yellow sapphire that even the best experienced jeweller is advised caution before he judges and values the stones.The most recent deception is yellow coloured synthetic cubic zirconia (popularly called American diamond) sold as natural yellow sapphire. Generally such type of stones are set in ring and the synthetic stone has a sparkling sub-admantine lustre that often tempts many people to buy the stone.
Another aspect the general public should know is that today yellow sapphires are treated to enhance their colour. Most of the treatments can be identified, but some require sophisticated laboratories to ascertain the genuinity of the colour. But what definitely can be checked up is whether the stone is a natural or synthetic or any other similar looking stone having different chemical composition.
Low budget stones range from few hundreds per carat to over a thousand rupees. Very high prices are demanded for yellow sapphire of over three carat with good colour. It is therefore advisable to test stones of high value before setting them in jewellery.
3. Blue SapphireThe name sapphire comes in to being from the usages of many civilizations. In Sanskrit it is called Sauriratna which means dedicated to “Saturn”. In Chaldean, it was called Sampir, in Greek Sappheiros (blue), in Latin Saphirus and in Arabic Safir.
Sapphire is the name given to all colours of corundum other then red. When used on its own, the name implies Blue sapphire. Blue sapphire is coloured by a combination of iron and titanium.
Innumerable superstitions are attached to this beautiful blue gem as it governs the planet “Saturn (Shani)” with Indian name “Neelam”. The blue sapphire is more common in the West than in the Orient. The best sapphires originate from Kashmir with their cornflower blue colour, the deep blue shade which one cannot forget if once observed.
In fact many fall prey to the same coloured synthetic gem which look very identical. There are cases where people have bought large sized beautiful bright blue Kashmir sapphires for an exorbitant sum. When tested them they were found to be ordinary synthetic blue spinels!Other blue coloured stones which could be mistaken for sapphire are Benitoite, Iolite, Spinel, Tourmaline, Tanzanite, Kyanite, Synthetic blue sapphire as well as synthetic blue spinel.
Blue sapphires undergo different treatments like heat, dyeing, irradiation, diffusion, glass filling etc. Blue sapphires are made synthetically by process like vernuil and flux melt and can be separated by inclusions.
The most important sapphire occurrence are Sri Lanka, Myanmar, Thailand, Tanzania, Cambodia, Australia, Malaysia and the state of Montana. Mining and extraction of sapphires are mainly from the alluvial deposits. Many places the primary and secondary deposits are seen simultaneously; the best examples for this are Myanmar, Umba Valley in Tanzania, Montana, as well as Kashmir Sapphires in India. The deposits in Australia, Thailand and Cambodia are in the alluvial rubbles found as a result of weathered volcanoes.
Top prices for blue sapphire are paid for stones of an intense blue verging on the violet. Large saapphires are more common then large rubies. Colour zoning can be a problem in sapphire; look for stones which have no major zoning problems. Many blue sapphires are too dark in colour, especially those from basalt sources such as Thailand and Australia. Such stones are generally inexpensive. Similarly, sapphires which are too light in colour are also inexpensive. The best stones are those which are well cut, eye clean and most importantly, with intense blue colours.
4. EmeraldBeryl family has many contributors to give various beautiful different colour-shades and its variations, but Chromium oxide is decisive for the creation of the most extravagant green colour in an Emerald. It is only those Beryls that have chromium and/or vanadium as colouring agents can be considered to be emeralds. Infact as per CIBJO rules it is only the chromium colour Beryls can be considered as Emeralds.
If the green colour of the beryl is dominantly of iron oxide, it is considered as green beryl. Even a minute trace and chromium is sufficient to create the unmistakable Emerald and colour that can easily distinguished from the green colour of the Beryl that is caused by iron oxide. The intensity of the green colour depends on the quantity of chromium present. The trace element of vanadium and iron creates the tones of yellow and bluish.
According to astrology emerald guards the interests of the planet Mercury (Budh).
Emerald is a very brittle stone containing fissures and can be easily chipped. It should be washed in mild soapy water and should not be never put in a ultrasonic cleaner.Natural emeralds contain inclusions like two phase, three phase, mica, pyrite, needle etc. These inclusions are very helpful in separating natural emeralds from its synthetic counterpart and other green gems.
Emeralds are often treated with oil (colourless or coloured) or resin which fills the cracks and fissures which reach the surface. Oiled emeralds often show colour patches in the fissures under the Microscope. Resin treatment is difficult to detect as many a time the refractive index of the polymer is very close to that of emerald. Under microscope the resin treated emeralds may show blue or orange flashes.
Emeralds can be simulated with synthetic emerald, quartz, fluorspar. Massive hydrogrossular garnet, glass etc.
The best emeralds come from Colombia. They have a unique shade and sparkle quality. Emeralds are also found in Brazil, Zimbabwe, Madagascar, Russia, Austria, Australia and India. Since emerald is a very brittle stone extra care has to be taken while setting the stone as well as while handling the stone during wearing or storing in the jewellery box.
Synthetic emeralds are produced in a large quantity and have a beautiful dark green colour. Since the technology that is used to produce the synthetic emerald closely resembles the natural stones identification is not very easy without proper instruments.
The price of the emerald depends on the shade of green. Deeper the green colour the price increases. The origin of emeralds is still a major price factor.
5. Chrysoberyl Cat’s eyeThe mineral chrysoberyl produces green, greenish yellow or brown colour gemstones. The cat’s eye variety of honey yellow to greenish or brownish yellow chrysoberyl is called as cymophane,. Owing to its peculiar optical property chrysoberyl cat’s eye has a prized position in jewellery.
Cat’s eye effect in gemstone is a streak of light which moves when the stone is turned, opening and closing like the eye of a cat.
The cat’s eye effect is seen in many types of gemstones species such as quartz, tourmaline, apatite, scapolite and diopside. The most popular and the prized one is the honey green to yellow variety of chrysoberyl (Lasuniya) showing this phenomenon.
The cat’s eye phenomenon is produced by the reflection from very fine tubular or needle like structures present inside the stone. The stones containing bundles of needles in parallel orientation reflect the external. When such a stone is cut in cabochon cut (hemispherical), then the stone appears to have a streak of white light.It resembles the pupil of a cat’s eye and especially the greenish yellow colour looks very similar to the feline eye.
Chrysoberyl cat’s eye can be easily simulated by apatite cat’s eye, quartz cat’s eye, sillimantie cat’s eye etc. It is essential that the jeweller can actually differentiate between these. While buying an individual stone particular attention should be paid to the centering of the white streak, the eye as it is called should be thin, hair-like and should move from one side to another through 1800. Of course such perfect stones demand their value and for those who need cat’s eye for lower budget, should expect the stone to have more translucency and thick streak of light with hardly any movement.
Chrysoberyl cats eye is one of the Navgraha stone representing Ketu. Mythologically chrysoberyl cat’s eye wards off the evil effects of the “Ketu”. In the recent times great demand is seen in the market for this stone. Main occurrence of Chrysoberyl cats eye are India (Orissa, Andhra Pradesh, Kerala and Madhya Pradesh), Brazil, Sri Lanka, Burma and Madagascar.
6. Hessonite GarnetThe honey coloured or the orange-brown stone in the Nine Gems is the Hessonite Garnet representing “Rahu”, popularly known in local markets as Gomed. This stone is said to guard the interests of the “Rahu”. Gemmologically the hessonite garnet is variety of grossular garnet. In fact the Garnet is a mineral series which include various coloured varieties, the most common being the purplish red variety called almandine pyrope. Rare varieties of garnets like hessonite, demantoid, tsavorite, spessartite etc. can demand high prices.
Hessonite is sometime known as “Cinnamon stones”. (from spice island of Sri Lanka) Hessonite garnet is common in the gem gravels of Sri Lanka. Individually the Hessonite garnet is a very durable stone generally showing granular types of inclusions or peculiar treacly streaks called as “treacle” which gives the stone from inside an oily appearance. Main occurrances of Hessonite are India, Sri Lanka, South AFtrica, Pakistan, USA, Brazil, Tanzania and Kenya.
7. CoralCoral is one of the Naagraha stone representing planet “Mars” (Mangal).
Coral scientifically known as Corallium nobile or Corallium rubram.
Coral is formed by coral polyp, a primitive type of plant like animal called a zoophyte. The composition of coral is almost wholly of Calcium carbonate with about 3 percent of magnesium carbonate is secreted by the animal. They grow as branching structures which look something like a leafless tree.
Thin section of coral shows dark red radii passing from the centre to the outside surface and these radial colour bands are seen on a longitudinal section as lines of pigment running parallel to the length of the section. These colour bands are clearly visible by eye of the surface of coral.The hardness of coral is about 3.5 on Moh’s scale and had a hackly type of fracture. Although soft in hardness they are reasonably tough and take a high polish. A spot of acid placed on the surface of coral will cause effervesces, which is a useful test for coral against its imitations.
Coral comes in different colour for which different names have been applied.
White to red coral Corallium rubrum White coral Oculinacea Vaseuclosa Black Coral Akabar or King’s coral Blue Coral Akori Coral (Allopara Subirolcea)
Coral gems with their hardness of 3 – 4 should be worn and cleaned gently. Warm water and mild detergent are best for cleaning and daily wearing of this gem in rings or bracelets is not advisable. The coral get damaged by exposure to acids and high heat and long exposure to water.
Today corals are artificially prepared by ceramic process or they are reconstructed resembling the natural material to a large extent.. Natural corals generally show wood grain effect, striations, pits and groove marks on their surface. Easiest test is to take a drop of diluted hydrochloric acid on needle point and place it on a most inconspicuous position of the gem. If the drop effervesces then it is coral. Reconstructed and dyed coral loses colour when tested with diluted HCL acid. The main occurrences of coral are Australia, Italy, West India, Japan, Philippines, India etc.
8. PearlOut of the priceless collections of gems, pearls are indeed the symbols of beauty, purity and wealth – the admiration of which has spread through every culture, in every age, over the development of many a civilization in the world.
Pearl is a word of mystery and magic for many people it gives rise to legends of mystical birth from the sea. Throughout history, Hindus and Arabs have been the greatest of admirer of pearls. Among the Hindus there is a belief that the pearls were dewdrops fallen at night into the sea and collected in the body of the oyster. They also attributed the pearl, the power of bringing good luck.
Astrologically pearl is considered to be representative for planet Mars ( Moon , Chandra).
Pearl is an organic substance and is the result of the biological process. Pearl is composed principally of mineral matter, nevertheless as this material is produced by animal life and hence it is considered as an organic product.Any shellfish is capable of producing a pearl under suitable conditions, but only those animals which have a shell with a pearly (nacreous) lining can form a lustrous pearl which is of a gem quality.
Without oyster or mussels there would be no pearls. The rich or poor harvest of pearls depends upon the oysters.
Various types of Pearls bearing oysters are :-
- Strombus Gigas
- The Unionides
All oysters are collectively called as Mollusc. The pearl bearing molluscs are delicate animals. For the purpose of protecting their delicate bodies they cover the interiors of their shells with a smooth lustrous material.
PARTS OF THE OYSTER’S BODY
- Mantle – The most important part of the oyster is the mantle as regard to pearl formation. The mantle is bounded on its outermost face by a layer of secretary cells, from these cells is secreted the shell forming substance. Actually when the animal is born there is no shell covering, it is this mantle tissue which starts oozing our three different substances which harden to form the shell.
- Shell – The shell of the oyster and fresh water mussels are composed of three main layers namely Pariostracum, Prismatic layer and Nacreous layer (mother of pearl). Fine quality pearls generally consist almost entirely of nacreous substance
From the point of view of the jewellery the two chief pearl forming animals are :-
- The pearl oyster is a marine water mollusc and gives us the oriental pearl or marine water pearl.
- The pearl mussel is a fresh water mollusc and produces fresh water pearl.
The chemical composition of pearl can vary according to its place of origin. In certain cases the quantity of organic material or of water is different. The beautiful lustre of pearls is known as the Orient of pearls.
CULTURING OF PEARLS
Cultured pearls are produced by the insertion in the pearl oyster an artificial nucleus, usually Mother – of – pearl. And the deposition of nacre thereon by the molluscCultured pearls are generally from Japan and China
METHODS OF TESTING PEARLS
- Endoscope Method
- Lauegram Method
EVALUATION OF PEARLS
Like any other gemstones, each pearl is different. Pearls are first sorted according to whether they can be used for industrial purpose or as a gem. In industry they are used mainly as cosmetic or medicine base. The gem group is then further categorized into various sections. Each section is then further sorted from the highest quality and price to the lowest quality and price.
The main grading considerations are:
- Thickness of the nacre
- Surface perfection
CARE OF PEARLS
Due to the softness of pearls, it requires to be handled carefully, worn carefully, regularly cleaned and examined. It should not be exposed to head, acids, solvents or detergents. It is necessary that all pearl necklaces should be regularly re-strung and knotted to prevent their rubbing against each other causing flat abrasions. Pearls should never to wrapped in a cotton wool because the heat generated would add to the drying out hazard. Direct application of perfume, talcum powder or face powder should be avoided on pearls. If pearls have not been worn for a long time they begin to look dull and lifeless, but their glow can be restored by gently rubbing a little olive oil and Tripoli (buffing) powder.
9. DiamondDiamonds have fascinated man since time immemorial. There has always been some mystery, intrigue, romance and royalty associated with this sparkling gem. Diamond is considered the king among gemstones, as it’s the hardest among known mineral.
The word “diamond” actually refers to its hardness (Greek – Adamas, unconquerable). There is nothing comparable to diamond in hardness; it is therefore nearly imperishable. Its cutting resistance is 140 times greater than that of corundum. However the hardness of a diamond is different in the individual crystal faces. This allows one to cut diamond with diamond (or diamond powder). Although it is the hardest, it can split easily along certain planes. You require extreme care during mounting because diamond has perfect cleavage.
Diamonds have the best quality of lustre known as adamantine. When properly cut and faceted a diamond can refract & reflect back 100% of the light falling on its surface giving the diamond a spectacular brilliance or life and a fire of rainbow colour display which can arrest anyone’s eye. It is this excellent lustre, life and fire that enables the experienced eye to differentiate between diamond and its imitations.
BIRTHSTONE FOR APRIL
The diamond is the traditional birthstone for the month of April, and a non-traditional birthstone for February, July, and October. People who were born under the sign of either Cancer or Libra sometimes claim the diamond as their astral stone, and astrologers have linked it to the planet Venus (Shukra). The diamond is your stone of celebration for the tenth and sixtieth anniversaries. Diamond stands for purity, peace of mind and tranquility. It inspires romance and creates confidence in the wearer.
HOW DIAMONDS ARE FORMED
Diamonds were created billions of years ago out of carbon deposits subjected to intense heat and pressure deep within the cavities of the Earth. It is said diamond is formed at a great depth of over 150 km. at a scorching temperature of 13000C under great pressure. The noble diamond is actually the simplest structure of all: crystallized carbon in cubic form. Thanks to the volcanic activity that brings them to the surface, diamonds may be found in rock structures mostly known as kimberlites.
Diamonds are found in primary and secondary deposits. Up to 1871 diamonds were only washed out of diamondiferous places. By chance a primary deposit was discovered in South Africa: Volcanic pipes filled with a diamond-bearing rock, kimberlite.
There are diamond deposits in many parts of the world, most occurring in Africa and Siberia. Up to the 18th century a few diamonds came from Borneo but most from India, where some large stones of historical value were found. The most famous mines were at Kollur near river Krishna in Golconda, Hyderabad in South of India where famous and historical diamonds including the Kohinoor, the Regent, the Great Mogul and the Tavenier Blue were found.
SOME OF THE FAMOUS DIAMONDS FOUND IN INDIA
1. Dresden (Green) 41 carats 2. Hope (Blue) 44.50 carats 3. Regent 140.50 carats 4. Sancy 55 carats 5. Tiffany 128.51 carats 6. Koh-i-noor 108.92 carats 7. Jacob 100 carats 8. Nassak 43.38 carats 9. Shah 88.70 carats 10. Florentine (Yellow) 137.27 carats
SIGNIFICANT SOURCES OF DIAMOND SUPPLY
The first diamond ever discovered in Africa was found by a young child walking on the beach. Although he did not know it then, this discovery in the 1860s would fuel the beginning of South Africa’s diamond era. South Africa became the world’s premier source of diamonds, a position the country enjoyed for about a century. Other significant sources include Congo (formed Zaire), Botswana, and parts of the former Soviet Union.
GRADING A DIAMOND THE 4 C’S
- Colour: Colour grading is done on the basis of its whiteness, absence of yellow, D to Z.
The absolutely colourless diamond is graded D and is considered the best among colourless diamonds. The further grades are E, F, G, H, I, J, K, onwards upto Z.
- Clarity: Clarity grading is done on the basis of its absence of inclusions. IF – I3
The diamond is formed deep inside the earth, at very high temperature and pressure and therefore it generally contains some flaws. Hence those diamonds without any flaws are considered to be of better quality. The Clarity grades are Internally Flawless, Very, Very Fine Inclusions (VVS), Very Fine Inclusions (VS), Small Inclusions (S1, S2) and the Pique or poor quality (P1, P2 P3 or I1, I2 I3).
- Cut: The most popular cut of all is called the brilliant cut, which consists f a minimum of fifty-eight facets. Many shapes lend themselves to the brilliant cut, but by far the most popular is the round. The brilliant cut actually can mask some flaws and imperfections otherwise visible to the naked eye, such as carbon spots, bubbles, and inclusions. Some flaws can even be cut right out of the stone during the cutting process, thus enabling the consumer to have a diamond with fewer flaws and a better appearance. Although it will usually be apparent to the naked eye, if you are uncertain of the cut and the number of facets in the diamond, be certain to inquire. This is more difficult to ascertain when buying a diamond cluster or band ring, for these stones are generally quite small. In the case of a ring consisting of smaller stones, it is preferable that the diamonds be classified as full cuts. This term simply refers to a diamond that is a round, brilliant – cut gem.
The brilliant is arguably the most popular cut, but the consumer is likely to encounter many others on the market. One variety that has always been a classic in the gem world is the step cut, which features faceting like steps on the perimeter of the stone. A rectangular shaped step-cut gem is often called an emerald cut. The step cut is frequently seen in combination with the brilliant cut. When faceted in this way, the rectangle is known as a radiant cut; when this same combination is found in a square-shaped gem, it is known as a princess cut.
- Carat: Carat is the unit of weight
200 milligram – 1 carat
5 Carats – 1 gram
Higher the carat weight higher the rate per carat.
COMMON SIMULANTS OF DIAMOND
Synthetic Cubic Zirconia
- Colour: Colour grading is done on the basis of its whiteness, absence of yellow, D to Z.