Properties

	Hardness : Diamond is a perfect “10”, defining the top of the hardness scale.
	Clarity : Diamond is transparent over a larger range of wavelengths (from the ultraviolet into the far infrared) than is any other substance.
	Thermal Conductivity : Diamond conducts heat better than anything else; - four times better than the copper.
	Melting Point : Diamond has the highest melting point (3820 degrees Kelvin)
	Lattice Density : The atoms of Diamond are packed closer together than the atoms of any other substance.
	Chemical composition : Almost pure carbon, crystallized under extremes of temperature and pressure.
	Colour : Diamonds come in a spectrum of colours from colourless to black. They may be transparent, translucent or opaque. Gem diamonds are primarily transparent and colourless. Most are tinged with colour, which, if sufficiently intense, are called as fancies. Blue and pink diamonds are the most valuable. Red diamonds are very rare. Clear white ones are called diamonds of the first water. Most industrial diamonds are gray or brown and are translucent or opaque.
	Optics : R.I.-2.417, Dispersion-0.044 (high).

Indian Occurrence
The principal diamond fields are in the states of Andhra Pradesh, Madhya Pradesh and Chhattisgarh and Orissa. In India, foreign companies commenced negotiations with State and Central Government mining authorities in 1994. Reconnaissance permits have since been granted in Andhra Pradesh and Chhattisgarh, whilst several applications are pending in other states. Reconnaissance fieldwork has commenced and is ongoing. To date, heavy mineral stream and loam sampling programmes have been completed and helicopter airborne surveys have been successfully undertaken.

Geological Occurrence
Diamond deposits can be classified as primary (kimberlites and lamproites) and secondary (alluvial and marine). As a primary mineral, diamond occurs only in olivine-rich peridotites, notably kimberlite, which is defined as a volatile-rich, potassic, ultrabasic igneous rock that occurs as small volcanic pipes, dykes and sills having olivines, magnetite, and phlogopite as major minerals. Substantial amounts of diamond are mined from both recent and ancient (consolidated conglo-merates) placer deposits.

Diamond Formation
Diamond and Kimberlite Sources
Diamonds are much older than their host kimberlites and are carried to the surface as accidental fragments, called xenocrysts and xenoliths, from the depth.

Diamond is the high-pressure mineral form of the element Carbon and generally forms in nature at depths greater than 150 kilometres and temperatures greater than 10000 C, within the upper mantle of the earth. Diamonds are old, with ages ranging from 1000 to 3300 million years.

Most carbon for diamond formation is derived from very deep earth fluids rich in CO2 (Carbon Dioxide) and CH4 (methane) and other carbon-bearing species. This carbon may be directly derived from the deep earth or recycled from shallower depths in subduction zones.

Kimberlite is the rock formed by a kimberlite volcanic eruption or intrusion and is the result of processes that caused the mantle to melt at great depth and this melt to be intruded to the earth’s surface. Kimberlites are younger than the diamonds they contain. The pipes of Kimberley are only 90 million years old and contain diamonds -3000 million years old.Diamonds occur in patches at depth in mantle rocks called peridotites (blue and green) and eclogites (orange) and therefore not all kimberlites contain diamonds. Kimberlites found within very old (>2500my) cold continental crust that is underlain by relatively cold mantle have the highest chance of containing diamonds. These areas on earth are prime targets for diamond exploration programs.

Eruption of a Kimberlite
Kimberlites blow a big hole in the land surface (the crater) and cut through solid country rock to form a steep pipe (the diatreme) that narrows and may become complex with depth (the root).

Kimberlites are extremely violent eruptions and incorporate fragments of deeper mantle and shallower crystal rocks. Diamonds are liberated from broken diamond-bearing mantle fragments (xenoliths) during the intrusion and eruption of the liquid kimberlite magma. They can be found at all levels within a kimberlite.

Secondary sources of Diamond
Kimberlites, like all rocks are continuouslly being worn down, broken and dispersed (erosion) by climatic agents like rainwater, rivers and wind.

As diamonds and other mantle minerals are dispersed into rivers they tend to accumulate in between pebbles and boulders forming the gravel bed of a river. These deposits are called alluvial gravels.

After hundreds or even thousands of kilometres, rivers end up in seas and the transported diamonds are deposited on gravely beaches. Sea or land level changes can result in diamondiferous marine deposits both onshore and offshore, as is the situation along the west coast of South Africa and Namibia.

The dispersal of diamonds from their primary sources into streams and rivers and ultimately to the sea is generally accompanied by an increase in average value per carat, as flawed stones are progressively destroyed with greater transport.

Only the best diamonds survive this long journey and that is why alluvial and marine diamonds are better in quality than average kimberlite pipe diamonds.

Exploration for Diamonds
The techniques applied in diamond exploration are :

	Geophysical Surveys Geophysical surveys comprising of magnetic, gravity, electrical, electromagnetic, and gamma ray spectrometry have been extensively applied for Kimberlite/lamproite exploration.
	Geochemical Surveys Geochemical prospecting is widely applied to locate kimberlites and assess the diamondiferous nature of the pipe. The major elemental chemistry of kimberlites similar to those of normal rich ultramafics expects the kimberlites usually enriched in TiO2, K2O, P2O5, and low MgO. Kimberlites have high K/Na and low Mg/Fe ratios, which distinguishes them from ultramafics. Trace elemental chemistry of kimberlites enrichment by 10 to 100 folds Li, Fe, P, Ti, Rb, Sr, Nb, Sn, Ba, Nd, Gd, Hf, Ta, Ti and Pb greater than 100 times C, Cs, La, Ce, Th and U. Kimberlite rock indicator mineral like diamond, ilmenite, chromite, chrome-diopside and pyrope garnet will help indirectly in locating the target areas for kimberlite bodies.
	Photo-Interpretation and Remote Sensing Techniques Aerial photographs and satellite imagery providing a synoptic view of the earth’s terrain, are being used by geologists to prepare basic geological maps and obtain geological information on which further detailed work can be planned in a speedy and cost- effective manner. Remote sensing techniques are widely applied in different segments of geological mapping and mineral investigations. They hold the key and if utilised properly, provide valuable and often vital information which can help in drawing correct inferences. Conjunctive use of remote sensing techniques with ground observations may workout to be a better strategy.

The need is for an integrated programmed comprising geological, Geophysical, Geochemical, Photogeological and remote sensing techniques. The combination of these techniques is a powerful exploration tool.

Beyond the Facts...

	Today, 75-80% of the world’s natural diamonds are used for industrial purposes and 20-25% for gemstones. It is the chemical and physical properties of this mineral that give it the superior cutting ability for industrial use.
	Diamond coatings have improved industrial applications in cutting and in aiding the performance of semi-conductors.
	It is the optical properties of this mineral that give it the superior beauty and durability to be used as a gem stone.
	The rarity of this gemstone is related to the petrogenesis of the igneous rock from which diamond is recovered.
	Diamond may even be found in meteorites.
	It is an important economic resource, responsible for developing nations and creating war.
	Faceting diamond, in order to maximize its optical properties, depends upon a knowledge of geometry. Diamond is the perfect mineral to focus on considering the fact that diamond studies cross disciplines, such as mineralogy, geology, astronomy, material science, mathematics, anthropology, art, history, and economics.

Fact : Exploring The Nature of Diamonds

	Although diamonds vary from colourless to black, most are tinged with yellow. Diamonds are often set in yellow gold to mask the yellow body colour. Nitrogen is believed to be responsible for diamond’s yellow colour and blue diamonds are coloured by boron. Carbon is adjacent to nitrogen and boron in the periodic table and substitution is possible because of size similarity of the elements.
	Diamond has a scratch hardness of 10 on the Mohs scale and therefore it is indestructible. In addition to a good cleavage, diamond can only be scratched by another diamond.
	Diamond often fluoresces blue and hence the historical “blue-white” colour designation given to colourless diamonds. Other fluorescent colours include orange and sometimes a bright yellowish-green.
	Diamond’s high refractive index gives it extraordinary brilliance, scintillation (sparkle), and adamantine luster. When choosing smaller diamonds, brilliance is the key factor.
	Diamond has an affinity for grease! This is helpful in separating mined diamonds but detrimental to keeping a diamond ring clean after washing greasy utensils.
	Thermal conductivity separates diamond from simulants. Not only is diamond’s thermal conductivity higher than other colourless gems, it is four times greater than copper!
	Inclusions are helpful to identify the rock within which diamonds formed and the age of the diamond. Although inclusions include garnet and diopside, the most common inclusion in diamond is diamond.
	Diamond mining began in India. Extensive mining shifted from India (17th century), to Brazil (18th century), to the African continent (19th century), and finally Australia and Canada (20th century). Today diamonds are mined in some 25 countries on every continent but Europe and Antarctica. The top seven producing countries, that account for 80% of the world’s rough diamond supply, are Australia, Botswana, Zaire, South Africa, Russia, Angola, and Namibia.
	Diamonds are employed by the lapidary (gem cutter) to shape and polish diamonds and other gems. Tiny holes drilled in diamonds are used to draw ductile metals like copper into extremely fine wire for the electronics industry. The stones are also used to true the surfaces of precision grinding wheels. In machine shops, tools tipped with diamonds perform precision-cutting tasks. Geologists and engineers use diamond-tipped hollow steel bits for drilling deep rock formation samples.
	SureBlade Diamond Scalpels have performed over 100 sequential surgical procedures with no reduction in sharpness. The last incision on the 100th procedure is as precise as the first incision on the first procedure. The diamond remains cold while infra-red energy heats the tissue to coagulation temperature. As a result, collateral tissue damage is minimized and there is less delay in re-vascularization. This results in less bruising with quicker healing and recovery.
	Synthetic diamonds were successfully created in the mid 1950s, produced on a commercial scale since 1960, and gem quality synthetics came into the market in the 1990s.

Synthetics
Synthetic diamond is produced under high pressure and temperature produced at low enough costs to be used as a natural diamond substitute. However, there are
indications that we may begin to see gem quality synthetic diamonds within the next few years. Synthetic diamond is used very extensively (two-thirds of the world production) for industrial purposes as abrasive diamond grit.

The Four C’s
The 4 Cs are cut, clarity, carat weight, and colour, and they are used to assign a financial value to diamond. To obtain a diamond within a certain price range, the four criteria will need to vary. Cut is the most important factor and should never be compromised. Therefore, a smaller carat weight might be necessary to stay within price range, if all other factors are also kept high.

1. Cut
When found or mined, diamonds look like fragments of glass. Two or more gems are usually cut from a rough stone. Diamond gems have been cut in many different shapes. The task of the highly skilled diamond cutter is to place the facets so that most light will reflect through the top facets. Diamond cutting is a great skill, practised for generations. The natural form of a diamond will determine the shape of the final polished diamond. A standard round brilliant cut, with 57 or 58 polished facets, is based on the original shape of an octahedral crystal. The traditional diamond cutting and trading centres are based in Antwerp, Mumbai, Tel Aviv, New York and Johannesburg. China and Thailand are more recently developed centres. Once polished, most diamonds are sold and traded in the 24 registered diamond bourses around the world.

	Cut height is the most important factor in a diamond’s brilliance.
	Since it’s all about light optics and the ideal angles to produce the maximum effect, the cut is critical to the beauty of the diamond.
	An deeply cut stone will also affect the way the light passes and reflected in the diamond.
	A shallow cut stone will seem dark, as the light exits the back of the stone, the angles not reflecting the light back up through the top of the stone to eyes

Some notable cuts are :

»	The Round Brilliant	»	Emerald Cut
»	Marquise	»	Pear Cut
»	Oval	»	Trillion Cut

2. Clarity
Flawless
It is the highest grade of gem stone, where no internal inclusions or surface imperfections are visible under 10x magnification.

Internally Flawless
It describes stones with no visible interior imperfection but having minor surface blemishes which do show under magnification. This top “perfect grade” is also extremely expensive.

Very Very Slight Imperfection
This Category (divided into “1” and “2” factors) rates stones that have tiny inclusions which are very difficult to detect even with 10x magnification. These tend to appear “perfect” to all, but the most trained professionals,

Very Slight Imperfection
This grade (divided into “1” and “2” factors) indicates very slight imperfections which are still difficult to see with 10x magnification. This grade of stones appears to all but the trained eye, as perfectly clear.

Slightly Included
This category diamonds have slight imperfections and inclusions visible under 10x magnification (divided into “1” and “2” factors). They represent one of the best values for a nice diamond.

Imperfect
The lower grades are the grades, with visible inclusions in the stone. The “Imperfect” range is divided into three factors (“1”, “2”, and “3”) with each factor indicating a stone more visibly included to the naked eye.

3. Carat
Carats are the traditional measuring unit of a diamond’s weight, one carat equaling 200 milligrams. A carat is divided into 100 cents, so the same diamond can be represented as weighing a carat and a half, 150 cents or 1.50 carats.

Is bigger always better?

	This is not at all true with the weight/size of diamonds.
	A big ugly stone isn’t better than a smaller eye clean one.
	The carat measurement indicates its weight.
	With each weight category increase (quarter, third, half), the value per carat of a diamond will increase significantly (given all have the same other factors).
	A stone which is twice as large as an otherwise identical smaller stone might be three or more times more expensive. Geometric increases at each weight category are to be expected,
	It’s often said these geometric price increases, as size increases, is true due to the “rarity” of top grade larger stones.

4. Colour
Generally, the less colour a diamond shows, the better it is. (There are exceptions like extremely valuable “fancy coloured diamonds” and less expensive enhanced “irradiated” stones). Generally speaking, grades “D” to “G” tend to appear colourless.

Various Diamond Colour Grading Systems
Diamond colour is graded across a scale, from a perfect colourless D to a markedly coloured Z. Almost any diamond will show a slight trace of colour, except for the very top grades, which are both rare and very expensive.

	For all practical purposes, diamonds graded from D through F are considered colourless. Subtle graduations from D through F do exist, and are measurable by a gemmologist using 10X magnification.
	Most diamonds sold are in the G through J range. While the untrained eye still sees these stones as colourless when mounted, they are graded as slightly tinted. “J” is more tinted than a “G” colour.
	Diamonds graded from K through M show visibly marked colour, and are classified as faintly tinted or coloured.
	From N through Z the colours are increasingly more dramatic.

Indian Diamond Cutting and Polishing Industry
Over the last 20 years India has increased the volume and value of diamonds processed by five times, making it the world’s dominant polishing centre.

About 70% of the world Diamonds are cut and polished in India. About 185 million carats valuing about Rs. 33,000 crore were imported and about Rs. 40,000 crore worth were exported after cutting and polishing, in 2003-04. The Indian industry was built on polishing lower-quality stones, in particular those classified as industrial quality 30 years ago, but now referred to as near-gem. Increasingly, India processes the full range of sizes and qualities of gemstones utilizing not only a very cheap and abundant work-force estimated at 700,000 persons, but also the latest technology and qualified technicians. They cut stones up to 10 carats in size, previously processed in traditional cutting centres, but the bulk of production is in small stones.

The main destination for India’s exports are USA, Hong Kong, Belgium and Japan.

The Diamond Pipeline, 2003

Rough Diamond Production	Rough Purchased for Production (polishing)	Value of Polished Ex-production	Polished Diamond Content in Retail Sales	Retail Sales of Diamond Jewellery
US$9.4 BN	US$9.8 BN	US$14.8 BN	US$15.8 BN	US$60.0 BN

Famous Diamonds

1. Cullinan
	Originally 3106 carat diamond and found in Premier Mine South Africa in 1905.
	Presented to the King of England in 1907. Cut into 9 major and 96 smaller brilliant cut diamonds.
	Cullinan I-The Great Star of South Africa, 530.20 cts, pear shape cut. The largest cut diamond on the world, mounted in the British Royal Sceptre and housed in the Tower of London.
	Cullinan II-317.40 carats cushion brilliant cut in the imperial crown of Britain.
	Cullinan III-94.40 carats, Pear cut, in the Queen’s crown.
	Cullinan IV-63.60 carats, with square brilliant cut
2. Victoria
	469 carats, African diamond,
	Cut into 184.50 carat -supposed to be in the Nizam’s collection
3. Victoria-I
	428.50 carat-De-beers product from South Africa,
	Cut into 228.50 carats
4. Regent
	410 carats, found near Kistna river
	Cut into 140.50 carats, cushion shaped brilliant cut.
	Presently in France
5. Kohinoor
	In the 14th century, was in Malwa
	With Shah Jahan
	Looted by Nadir Shah in 1739, but taken back by Maharaja Ranjeet Singh
	Finally taken to England, where it was from 186 carats to 108.93 carats.
	Presently in the Imperial crown.
6. Orloff
	199.60 carat Indian diamond, was the eye of a Hindu Idol at Mysore,
	Presently in Russia.
7. Nizam
	40 carat Indian diamond
	Cut into 277 carats, supposed to be in the Nizam’s collection
8. The Great Moghoul
	787.50 carat, 7th century diamond, product of Golkonda,
	Finally cut into 280 carat diamond.
	Nadir Shah looted it in 1739 from Delhi
9. Darya-i-Noor
	186 carat, rectangular Indian diamond,
	Looted by Nadir Shah in 1739 from Delhi
10. Taj-e-Mah
	146 carat rose cut Indian diamond,
	Looted by Nadir Shah in 1739 from Delhi.

The views expressed here are solely of the author and not of the NMDC.

For further information contact
Mr. A. K. Gupta / Mr. R. K. Garg
N.M.D.C. Ltd., Panna Diamond Mining Project,
Panna-488 001. (M.P.) Tel. : 07732-271474