Gemstones

LEARN WHY TO WEAR NATURAL GEMSTONES AND THEIR PROPERTIES TO DIFFERENTIATE BETWEEN NATURAL AND SYNTHETIC GEMSTONES WITH SCIENTIFIC POINT OF VIEW

Gemstones are a product of earth. Some like diamond and zircon were found in deep in the earth and brought to the surface by explosion of molten rocks. Many like topaz, tourmaline and aquamarine, crystallized slowly from hot fluid and gases as they cooled and solidified, far below the surface of the earth. Other formed from liquid filtered in to cracks and pockets in rock, some formed when rocks were heated and pressurized by earth movements.


When we speak about gemstones , we usually means minerals that have been cut and polished and organic materials like corals, pearls, amber and ivory have been fashioned. Not all minerals are suitable for gemstone. A mineral must possess hardness and stability and occur in crystals or masses large enough for cutting.


If we analysis according to astrology everybody should wear natural gemstones. Gemstones work on aura, energy levels and minerals balance on our body. A 100% natural gemstone can do work on these things not a synthetic or treated one. As we know in the past, Kings and Queens always had worn their lucky gemstone on their (forehead) third eye location in the Crown. But we can’t wear in the Crown because of over all look issue of our personality. That’s why some ancient astrologers suggested some specific fingers according to planet situation.


 In today’s world trading of many precious gemstones and semi precious gemstones is replaced by treated or synthetic gemstones.  
A synthetic material is referred as a material which has natural counterpart; its chemical, physical and optical properties are same as that of its natural counterpart.


A synthetic gemstone is lab created product which is cheaper and clearer than the natural gemstone. The conditions are created in the laboratory are same as that of natural process .The formation time is different and hence natural can be differentiated from synthetics on the basis of its inclusion.


Synthetic gem material can be created from melt, solution, vapor or chemical precipitation. A simulant refer to a material which is similar in appearance to the gemstone it imitates .Its chemical and physical properties are not same as the gemstone imitates. A simulant can either be natural or synthetic .For instance Almandine garnet is a natural simulant for ruby while synthetic blue spinel is synthetic simulant for blue sapphire.


HOW WE JUDGE PRICE OF GEMSTONE AS PER THEIR QUALITIES?
The main characteristics are:
Beauty
Durability
Rarity
Luster
Optical effects


BEAUTY:
When we talk about beauty of gemstones .we refer to a combination of different attributes:
COLOR: The color is one of the most important factors which affect the quality and price of gemstone. Where colored gemstones are concerned the deeper the color along with transparency; it would fetch a higher price. But this is not the case of Diamond. For the diamond the colorless the diamond, the better is its price.
CUT: The beauty of gemstone is directly related to its cut. The actual beauty of gemstone is revealed only when it is cut and polished; the gemstone which is cut with proper proportion and angle will reveal all its effects like, fire, brilliance to its fullest. In case of diamond the beauty of diamond is fully depend upon its cutting.
CLARITY: Clarity of gemstone refers to absence of internal flaws. The price of gemstone depends upon its clarity. Again there is an exception to this law for amber. Here, the inclusion is the beauty of this gemstone .The amber which contains the inclusion like trapped insect, flowers, leaves, etc.
CARAT WEIGHT:  This is the unit used to measure the weight of the gemstone. A gemstone weighing more will be more attractive than the same gemstone of the smaller size. But make sure that the gemstone is natural not synthetic.


DURABILITY

This refers to the power of a gemstone to resist daily wear and tear. The durability of gemstones depends on following factors:
HARDNESS: The power of a mineral to resist external abrasion when a pointed fragment of another substance is drawn across it without sufficient pressure to develop cleavage is referred to as hardness. The harder the gemstone, the more durable it is. Diamond is the hardest gemstone.
TOUGHNESS: The durability is also depending on toughness of gemstone. The tough the gemstone, the more durable it is.
CLEAVAGE: Cleavage refers to the property of a crystalline material to split in a definite direction to give more or less smooth surface. A gemstone possessing cleavage would be less durable than the gemstone in which cleavage is absent.


RARITY
It is third and important character which a gem must possess. A gem of dark color and good transparency is rare, thus the demand is more. Rare a gemstone is, higher the demand and value. For instance emerald with light color is easily available so its price is low. But emerald with deep color and good transparency is not easily available which make then expensive.


LUSTER
The luster of a gemstone is comprised of the quantity and quality of the light reflected from its surface. There is an inherent potential luster possible for each pieces and variety of gemstones. Gemstone also valued as per there luster. Some gemstones have different luster to one another like:
 Diamond: “Adam tine” derived from the Greek word “Adamas” is the highest possible luster in gemstones and is possessed only by diamond.
ZIRCON: “sub admantine”the next lower on the scale and found gemstones that have high refractive index.
JADE: “Greasy” it has an oily appearance and texture, a typical luster of jade.
RUBY: Vitreous/glassy is the luster of polished glass and maximum number of gemstones possess this luster.
TURQUOISE: “Waxy” is the luster resembles the candle wax.
AMBER:”Resinous “the shiny luster of resin.
TIGER EYE: “Silky” this luster resembles to the fiber of silk.
PEARL: “Pearly” is the luster that produces a kind of shimmering glow.


Optical Effects
Optical effect in gemstone is just a decoration on the already beautiful gemstones. The optical effect enhances the beauty of gemstone. These effects are seen due to the reflection of light rays from beneath the surface due to presence of inclusions, also termed as sheen. Different types of optical effects are as follows:


CHATOYANCY: The term “CHATOYANCY “comes from the French “chat”, which means cat and “oeil”, which means eye. For, this reason, this phenomenon is also known as cat’s eye effect. This effect is caused due to reflection of light from the one directional parallel fibrous/needle like inclusions oriented in the gemstone. This moving band is always perpendicular to the direction of the inclusions. Cat eye is best seen under sunlight or other strong light source.


ASTERISM: This is also an optional effect seen in certain gemstone. Asterism is originated from the word aster meaning Star, Hence also known as the star effect.


This effect is seen due to the reflection of light from two/ three directional intersecting fibrous/needle like inclusions oriented beneath the surface of the gemstone, also termed as silk inclusion.


Asterism could be four – ray, six –ray or twelve-ray depending upon the number of direction of the inclusions.


Two direction intersecting fibrous/needle like inclusions would form a four ray star as in Almandine garnet.


Three direction intersecting fibrous/needle like inclusion would form a six ray star as in Rubies and sapphires.


The sharpness of the star depends on the thickness and compactness of the inclusion oriented in the gemstone. The finer and closely spaced inclusions would form a sharp star and vice -versa  


ADULARESCENCE: The milky, bluish/white sheen named as adularescence in moonstone appears to float along the transparent body. Thus the phenomenon adularescence seems to be move around the body of the stone when it is turned. The name adularescence derives from “adularia”. Because the moonstone which posses the phenomenon mainly historically known as “adularia”.
The structural pattern of the gem is the reason of this distinct optical phenomenon. It is due to the combination of orthoclase and albite feldspar which are arranged in layers. interference effect of light occurs due to these layers. Reflected light scatters equally in all spectral regions and produce a schiller. The color of schiller may be white, blue or blue and orange by this phenomenon. But the valuable as well as desirable color of schiller is blue, which is usually produced by a white or gray body colored stone.


PLAY OF COLOR: Play of color is unique special optical phenomenon. This phenomenon is usually exhibits by the gem opal. Opal is an amorphous form of silica and water. It is made up of microscopic spheres of silica. The transparent spheres of silica. The transparent spheres of amorphous silica and the voids between them having 3 dimensional cubic lattices produce a 3 dimensional diffraction grating. This structural pattern is the reason of interference and diffraction of light from the interior of gemstone.  The size of the spheres decides the longest wavelength of light which can be diffracted .thus, regular sheets of small spheres may only diffract blue light and not the other colors. Larger spheres may diffract green, blue and violet while still larger spheres may give red light and all other colors of shorter wavelength.


LABRADORESCENCE: Iridescence flashes of colors, which appear on the surface of the labradorite feldspar is known as “Labradorescence “. Labradorescence is an exclusive optical phenomenon that has solely shown by the feldspar gem Labradorite. The bright and beautiful display of labradorescence changes with movement of the stone.


Labradorescence Phenomenon is the interference of light in labradorite is caused by fine lamellae of repeated twinning. Some color effect produced by the platy inclusions made up of black magnetite or ilmenite. Due to this structure interference and diffraction of light occurs, when it passes through the gemstone and reflects from the parallel surface.


CHANGE OF COLOR:  Color change is a distinct optical phenomenon. In this phenomenon the gemstone is changes its body color distinctly under different lightning conditions, such as incandescent light to day light. It is referred as “Alexandrite effect”. This phenomenon also occurs in other gemstone like sapphires, garnet, tourmaline, etc. Gems change their color according to the nature of the light in which they are seen. Alexandrite appear green and bluish green in daylight and in incandescent light it appears as purplish red. Due to their chemistry color change gems absorbs colors, such as red and green .so these colors reflected from the gem and we see the colors. Usually the ranges of changing color are from green to yellow, brownish red to purple, yellow green to bluish green. Color changes factor justify the value and beauty of the stone the particular colors noted in the stone are very important for these, more visible color change adds more value for the stone.


AVENTURESCENCE: This is another optical effect which is a consequence of reflection of light from inclusions within the gemstone. When disk or plate- like inclusions of another mineral are present, and are of highly reflective nature such that they act as tiny mirrors, the gems sparkles and glitters. This glitter is called aventurescence. This effect is best seen in Green Aventurine Quartz. This gemstone is basically colorless and contains dark green mica flakes which give the gemstone its color and also the optical effect. Aventurescence is also known as the glittery effect.


ORIENT: Basically the luster of pearl is known as oreint, it is caused due to combination of two optical effects. These are breaking up of white light into minute spectra by diffraction caused by the irregular edges of the overlapping platy crystals of aragonite, and by the interference of light at thin films given by the same platelets.


INCLUSION IN GEMSTONE
The most useful internal features of gemstones are its inclusions. In natural gemstones they can be into three basic types:
Proto-genetic or pre -existing inclusions: These consist of minerals, which were present before host crystal began to form. Apatite in corundum, mica in Quartz and Emerald, rutile in Quartz, diamond crystal in diamond itself are common example of this type.
Syngenetic or contemporary inclusions: These consist of materials, which were present at the same time as the host crystal formed.


The Syngenetic inclusions are further sub divided into three types
Solid or crystalline inclusions
Liquid inclusions
Gas inclusions


Common crystal inclusions are solid crystals of the same or of other substance e.g. rutile needles in corundum, olivine in diamond, spinel crystal in spinel etc.


Liquid inclusions can be present as a trapped liquid inclusion or as a liquid trapped in a fracture, which has then sealed by the host.
Gas inclusions may be the bubbles of air. Air bubbles are mainly found in the glass, synthetic stones made verneuil and crystal pulling method.


Epi-genetic inclusions: These inclusions are formed after the formation of host crystal. They include there crystallization in fractures of foreign materials. The development of asterism by titanium dioxide in corundum is one of the best examples of this type of inclusion.

OTHER TYPES OF INCLUSIONS IN NATURAL GEMSTONES
Solid inclusion: A solid crystal or mineral fragment present in the gemstone is referred as a solid/crystalline inclusion. It can be seen in any natural gemstone like Diamond, Ruby, and Sapphire etc.


Liquid feather: These inclusions are frequently seen in natural ruby and sapphire. They resemble numerous slim, elongated tubes. Some are longer, some shorter, but all tend to point in the same direction and lie in a plane.


Two phase: A liquid which has a solid/crystalline or a gas bubble trapped in it is referred as a two phase inclusion. This type of inclusion is generally seen Topaz.


Three phase: A liquid which has a solid/crystalline as well as gas bubble trapped in it is termed as three phase inclusion. This is best seen in Columbian emerald.


Rain inclusion: These are basically two phase inclusions, which appear like rain drops. These inclusions are parallel and arranged in one direction. It occurs in beryl.


Color  Zoning :  A term refers to uneven distribution of color. Inclusions often appear as whitish or colorless parallel planets. Zoning is frequently observed in Natural ruby, Sapphire, Amethyst and Citrine.


Silk inclusion: This inclusion is seen as intersecting needle like crystal that has the similar appearance of the silk fabric when examine with reflected light. This inclusion is best seen in Natural corundum and Almandine garnet.


Parting planes: These are basically twinning plains which intersect each other and are placed at equal distance. One direction is very prominent while the other direction is weak. Parting planes are best scene in Natural corundum.


Zircon haloes: These inclusions look like haloes encircling a dark spot. They are actually tension cracks radiating from a zircon crystal due to radioactivity, which is dark crystal in the center. Example: Natural corundum.


Horse tail: Rare green demantoid garnet contains fine fiber like inclusions of the mineral asbestos. These inclusions are often tufted and resemble a horse’s tail.


Needle like/fiber: Inclusions of long, thin crystals that resemble needles or thin fibers. Often long thin crystals of Rutile, as in Rutilated Quartz, or Tourmaline, can be seen in Garnet, Sapphire, and Ruby.


Heat wave effect : The stones show a trickily appearance owing to the inclusions of small many transparent crystals having rounded outlines or fused aspect, and which are often accompanied by peculiar or treacle streaks which give to the stone’s interior an oily appearance. Example; Hessonite garnet.


Trichites: Fine liquid filled capillaries or hair like tubes, which reflects like mirror are termed as Trichites.
This is best seen in Tourmalines.
Lily pad: These inclusions refer to the halo of liquid with a crystal at the centre. It is best in Peridot.
Zebra stripes: This is basically liquid inclusion which has the appearance of the strips on the body of zebra and hence its name. It is generally found in Amethyst quartz.


Doubling of back facet edges: Due to high birefringence in gemstones, its rear facet edges appear double. This is referred as doubling of back facet edges. This is best seen in Calcite, Zircon, Peridot, Synthetic moissanite, etc.
Negative crystal: This is a cavity with a distinctive crystal shape. These are interesting because what you see is really just an outline. However, the outline will always show the same shape as that of the crystal form of the host material. It is often seen in Topaz and Quartz.