Gemstones

A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. The biggest pebble here is 40 mm long (1.6 inches).

A gemstone or gem (also called a precious or semi-precious stone) is a piece of attractive mineral, which—when cut and polished—is used to make jewelry or other adornments.^[1] However certain rocks, (such as lapis-lazuli) and organic materials (such as amber or jet) are not minerals, but are still used for jewelry, and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their lustre or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone.

Characteristics and classification

Gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al₂O₃). Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example diamonds, which have a cubic crystal system, are often found as octahedrons.

Gemstones are classified into different groups, species, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Emerald (green), aquamarine (blue), bixbite (red), goshenite (colorless), heliodor (yellow), and morganite (pink) are all varieties of the mineral species beryl.

Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and luster. They may exhibit pleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum.

Material or flaws within a stone may be present as inclusions.

Value of gemstones

Jewelry made with amber

There are no universally accepted grading systems for any gemstone other than white (colorless) diamond. Diamonds are graded using a system developed by the Gemological Institute of America (GIA) in the early 1950s. Historically all gemstones were graded using the naked eye. The GIA system included a major innovation, the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye (assuming 20/20 vision).

For the past several hundred years, gemstones have been broken down into two categories; precious and semi-precious. Though today we think primarily of diamond, ruby, sapphire, and emerald as "precious", these categories are based mainly on fashion and the composition of these two lists has changed frequently over time. As an example, while garnets are relatively inexpensive, a green garnet called Tsavorite, can be far more valuable that an mid-quality emerald.

A mnemonic device, the "four C's" (color, cut, clarity and carat), has been introduced to help the consumer understand the factors used to grade a diamond. With modification these categories can be useful in understanding the grading of all gemstones. The four criteria carry different weight depending upon whether they are applied to colored gemstones or to colorless diamond. In diamonds, cut is the primary determinant of value followed by clarity and color. Diamonds are meant to sparkle, to break down light into its constituent rainbow colors (dispersion) chop it up into bright little pieces (scintillation) and deliver it to the eye (brilliance). In its rough crystalline form, a diamond will do none of these things, it requires proper fashioning and this is called "cut". In gemstones that have color, including colored diamonds, it is the purity and beauty of that color that is the primary determinant of quality.

Physical characteristics that make a colored stone valuable are color, clarity to a lesser extent (emeralds will always have a number of inclusions), cut, unusual optical phenomena within the stone such as color zoning, and asteria (star effects). The Greeks for example greatly valued asteria in gemstones, which were regarded as a powerful love charm, and Helen of Troy was known to have worn star-corundum.

A factor in determining the value of a gemstone is called water. Water is an archaic term that refers to the combination of color and transparency in gemstones; used hierarchically: first water (gem of the finest water), second water, third water, byewater.

Historically gemstones were classified into precious stones and semi-precious stones. Because such a definition can change over time and vary with culture, it has always been a difficult matter to determine what constitutes precious stones.

Aside from the diamond, the ruby, sapphire, emerald, pearl (strictly speaking not a gemstone) and opal  have also been considered to be precious. Up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a precious stone as well, going back to ancient Greece. Even in the last century certain stones such as aquamarine, peridot and cat's eye have been popular and hence been regarded as precious.

Nowadays such a distinction is no longer made by the trade.  Many gemstones are used in even the most expensive jewelry, depending on the brand name of the designer, fashion trends, market supply, treatments etc. Nevertheless, diamonds, rubies, sapphires and emeralds still have a reputation that exceeds those of other gemstones.

Rare or unusual gemstones, generally meant to include those gemstones which occur so infrequently in gem quality that they are scarcely known except to connoisseurs, include andalusite, axinite, cassiterite, clinohumite and bixbite.

Gems prices can fluctuate heavily (such as those of tanzanite over the years) or can be quite stable (such as those of diamonds). In general per carat prices of larger stones are higher than those of smaller stones, but popularity of certain sizes of stone can affect prices. Typically prices can range from 1USD/carat for a normal amethyst to 20,000-50,000USD for a collector's three carat pigeon-blood almost "perfect" ruby.

Grading

Enamelled gold, amethyst and pearl pendant, about 1880, Pasquale Novissimo (1844 — 1914), V&A Museum number M.36-1928

In the last two decades there has been a proliferation of certification for gemstones. There are a number of  laboratories which grade and provide reports on diamonds. As there is no universally accepted grading system for colored gemstones, only one laboratory, AGL (see below) grades gemstones for quality using a proprietary system developed by the lab.

• International Gemological Institute (IGI), independent laboratory for grading and evaluation of diamonds, jewellery and colored stones.
• Gemological Institute of America (GIA), the main provider of education services and diamond grading reports
• American Gemological Society (AGS) is not as widely recognized nor as old as the GIA.
• American Gem Trade Laboratory which is part of the American Gem Trade Association (AGTA) a trade organization of jewelers and dealers of colored stones.
• American Gemological Laboratories (AGL) which has been taken over by "Collector's Universe" a NASDAQ listed company which specializes in certification of collectables such as coins and stamps
• European Gemological Laboratory (EGL) founded in 1974 by Guy Margel in Belgium.
• Gemological Association of All Japan (GAAJ), aka Zenhokyo, Japan, active in gemological research
• Gemmological Institute of Thailand (GIT) is closely related to Chulalongkorn University
• Asian Institute of Gemmological Sciences (AIGS), the oldest gemological institute in South East Asia, involved in gemological education and gem testing
• Swiss Gemmological Institute (SSEF), founded by Prof. Henry Hänni, focusing on coloured gemstones and the identification of natural pearls
• Gübelin Gem Lab, the traditional Swiss lab founded by the famous Dr. Eduard Gübelin. Their reports are widely considered as the ultimate judgement on high-end pearls, coloured gemstones and diamonds

Each laboratory has its own methodology to evaluate gemstones. Consequently a stone can be called "pink" by one lab while another lab calls it "Padparadscha". One lab can conclude a stone is untreated, while another lab concludes that it is heat treated  To minimise such differences, seven of the most respected labs, i.e. AGTA-GTL (New York), CISGEM (Milano), GAAJ (Tokyo), GIA (Carlsbad), GIT (Bangkok), Gübelin (Lucerne) and SSEF (Basel), have established the Laboratory Manual Harmonisation Committee (LMHC), aiming at the standardisation of wording on reports and certain analytical methods and interpretation of results. Country of origin has sometimes been difficult to find agreement on due to the constant discovery of new locations. Moreover determining a "country of origin" is much more difficult than determining other aspects of a gem (such as cut, clarity etc.)

Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate

Cutting and polishing

Raw gemstones

Rural Thai Gem Cutter

A few gemstones are used as gems in the crystal or other form in which they are found. Most however, are cut and polished for usage as jewelry. The picture to the left is of a rural, commercial cutting operation in Thailand. This small factory cuts thousands of carats of sapphire annually. The two main classifications are stones cut as smooth, dome shaped stones called cabochons, and stones which are cut with a faceting machine by polishing small flat windows called facets at regular intervals at exact angles.

Stones which are opaque such as opal, turquoise, variscite, etc. are commonly cut as cabochons. These gems are designed to show the stone's color or surface properties as in opal and star sapphires. Grinding wheels and polishing agents are used to grind, shape and polish the smooth dome shape of the stones.

Gems which are transparent are normally faceted, a method which shows the optical properties of the stone’s interior to its best advantage by maximizing reflected light which is perceived by the viewer as sparkle. There are many commonly used shapes for faceted stones. The facets must be cut at the proper angles, which varies depending on the optical properties of the gem. If the angles are too steep or too shallow, the light will pass through and not be reflected back toward the viewer. The faceting machine is used to hold the stone onto a flat lap for cutting and polishing the flat facets.Rarely, some cutters use special curved laps to cut and polish curved facets.

 Gemstone color

Color is the most obvious and attractive feature of gemstones. The color of any material is due to the nature of light itself. Daylight, often called white light, is actually a mixture of different colors of light. When light passes through a material, some of the light may be absorbed, while the rest passes through. The part that is not absorbed reaches the eye as white light minus the absorbed colors. A ruby appears red because it absorbs all the other colors of white light - blue, yellow, green, etc. - except red.

The same material can exhibit different colors. For example ruby and sapphire have the same chemical composition (both are corundum) but exhibit different colors. Even the same gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called "Padparadscha sapphire".

This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition, they are not exactly the same. Every now and then an atom is replaced by a completely different atom (and this could be as few as one in a million atoms). These so called impurities are sufficient to absorb certain colors and leave the other colors unaffected.

As an example: beryl, which is colorless in its pure mineral form, becomes emerald with chromium impurities. If you add manganese instead of chromium, beryl becomes pink morganite. With iron, it becomes aquamarine.

Some gemstone treatments make use of the fact that these impurities can be "manipulated", thus changing the color of the gem.

 Treatments applied to gemstones

Gemstones are often treated to enhance the color or clarity of the stone. Depending on the type and extent of treatment, they can affect the value of the stone. Some treatments are used widely because the resulting gem is stable, while others are not accepted most commonly because the gem color is unstable and may revert to the original tone.

Heat

Treble clef with gemstones

Heat can improve gemstone color or clarity. The heating process has been well known to gem miners and cutters for centuries, and in many stone types heating is a common practice. Most citrine is made by heating amethyst, and partial heating with a strong gradient results in ametrine - a stone partly amethyst and partly citrine. Much aquamarine is heat treated to remove yellow tones and change the green color into the more desirable blue or enhance its existing blue color to a purer blue.

Nearly all tanzanite is heated at low temperatures to remove brown undertones and give a more desirable blue/purple color. A considerable portion of all sapphire and ruby is treated with a variety of heat treatments to improve both color and clarity.

When jewelry containing diamonds is heated (for repairs) the diamond should be protected with boracic acid; otherwise the diamond (which is pure carbon) could be burned on the surface or even burned completely up. When jewelry containing sapphires or rubies is heated (for repairs) it should not be coated with boracic acid or any other substance, as this can etch the surface; it does not have to be "protected" like a diamond.

 Radiation

Virtually all blue topaz, both the lighter and the darker blue shades such as "London" blue, has been irradiated to change the color from white to blue. Some improperly handled gems which do not pass through normal legal channels may have a slight residual radiation^{[citation needed]}, though strong requirements on imported stones are in place to ensure public safety. Most greened quartz (Oro Verde) is also irradiated to achieve the yellow-green color.

 Waxing/oiling

Emeralds containing natural fissures are sometimes filled with wax or oil to disguise them. This wax or oil is also colored to make the emerald appear of better color as well as clarity. Turquoise is also commonly treated in a similar manner.

Fracture filling

Fracture filling has been in use with different gemstones such as diamonds, emeralds and sapphires. In 2006 "glass filled rubies" received publicity. Rubies over 10 carat (2 g) with large fractures were filled with lead glass, thus dramatically improving the appearance (of larger rubies in particular). Such treatments are fairly easy to detect.

 Synthetic and artificial gemstones

Some gemstones are manufactured to imitate other gemstones. For example, cubic zirconia is a synthetic diamond simulant composed of zirconium oxide. Moissanite is another example. The imitations copy the look and color of the real stone but possess neither their chemical nor physical characteristics.

However, lab created gemstones are not imitations. For example, diamonds, ruby, sapphires and emeralds have been manufactured in labs to possess identical chemical and physical characteristics to the naturally occurring variety. Synthetic (lab created) corundums, including ruby and sapphire, are very common and they cost only a fraction of the natural stones. Smaller synthetic diamonds have been manufactured in large quantities as industrial abrasives. Larger synthetic diamonds of gemstone quality, especially of the colored variety, are also manufactured.^{[citation needed]}

Whether a gemstone is a natural stone or a lab-created (synthetic) stone, the characteristics of each are the same. Lab-created stones tend to have a more vivid color to them, as impurities are not present in a lab, so therefore do not affect the clarity or color of the stone. However, natural gemstones are still considered more valuable on average due to their relative scarcity.

Navagraha

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Graha (from Sanskrit ग्रह gráha—seizing, laying hold of, holding is a 'cosmic influencer' on the living beings of mother Bhumidevi (earth). In Hindu Astrology, the Navagraha (Sanskrit: नवग्रह, nine seizers or nine influencers) are some of these major influencers.

"The Sanskrit word captures the idea that these nine grahas are living energies which put out waves of energy. These waves of energy affect our awareness. ... this indicates ... the active power of these celestial energies to seize our consciousness when we come under their influence or to take hold of what we focus on."

Accordingly to some, Grahas are the "markers of influence", that point out the karmic influence on the behavior of living beings. They themselves are not causative elements but can be compared to traffic signs.

Unfortunately, the term Graha was linked to the term "planet" of our solar system, as five members of Navagraha (the nine grahas) happen to be planets; but the Surya (sun), Chandra (moon), Rahu (north or ascending lunar node) and Ketu (south or descending lunar node) are not "planets" according to modern astronomy. This misconception is sometimes used as arguments against the validity of astrology.However, a fact common to all the navagraha is that they have relative movement with respect to the background of fixed stars in the zodiac.

"Graha" is sometimes also translated as "celestial body", but Rahu and Ketu are not celestial bodies either, but are only positions in the lunar path. A third translation is celestial god or demi-god, but again, Rahu and Ketu are demonic Asuras , not benign deities like Devas. Thus the term 'graha' in this contexts applies to the nine (9) planetary or cosmic deities, spirits, spiritual beings-entities, etc. The term however mostly refers to any spirit(ual) force in general.

Indeed, according to the astrological treatise Prasna Marga there are many other spiritual entities called grahas or spirits. All (excepting the navgrahas) are said to have been born of the anger of Lord Shiva or Rudra. Most grahas are generally malefic in nature but there are a few that may be good The book called The Puranic Encyclopedia, under the heading 'Graha Pinda', gives a list of such grahas (spirits or spiritual entities, etc), that are said to afflict children, etc. Also in the same book in various places the names of spirits (grahas) are given, like 'Skhanda graha' that is said to cause miscarriage(s),

 Connections to energies/mantras

Reports of psychics / energy readers affirm that Grahas are causing direct energy influence upon the auras (energy bodies) and minds of beings connected to the Earth (like humans, animals, plants etc.) Each Graha carries a specific energy quality, which is described in an allegorical form through its scriptural and astrological references. "... cosmic energy we always receive contains different energies coming from different celestial bodies..." The energies of the Grahas are getting connected in a specific way to the individual auras of humans at the time they take their first breath in a given nativity. These energy connections remain with the natives of Earth as long as their current body lives. "... The nine planets are transmitters of universal, archetypal energy. The qualities of each planet help to maintain the overall balance of polarities in both the macrocosmic and the microcosmic universe - as above, so below..." ^[8] Earth (as an independent energy entity) and its rotation around its axis is an important mediator and deciding factor of how these influences are carried out upon the beings, who are the children of Earth. See more in the Jyotisha Bhavas (also as a section under Hindu Astrology) . Humans are also capable to tune themselves to the chosen energy of a specific Graha through Samyama with that Graha or its presiding deity. The effects of worship of specific deities are manifested accordingly to the layout of their relative energies in a given nativity of a worshipper in question. "... When we repeatedly utter a Mantra we are tuning to a particular frequency and this frequency establishes a contact with the cosmic energy and drags it into our body and surroundings..."

The idea of planets, stars and other celestial bodies being the living energy entities influencing the other beings of the Universe has cross-references in many ancient cultures and had become the background of numerous modern fiction works (like Solaris by Stanisław Lem, see also the movie with the same title).

 Worship

The Navagraha are personified as celestial beings and worshipped as deities.

The worship of Sun (the king of the Grahas) as a personified being is common for most of ancient religions and spiritual traditions, Hinduism being a bright example of it. Many of classical Jyotisha scriptures (like Brihat Parashara Hora Shastra, Kalyana Varma's Saravali etc. etc.) start with an invocation of Sun-God (Surya). Other Grahas are commonly considered to be the living members of Surya's court and are being addressed personally in order to gain help in their respective areas of influence.

In several parts of India, there are clusters of Navagraha temples. One such cluster is near the town of Kumbakonam, Tamil Nadu; another temple is in Guwahati, Assam.

Navagraha, The British Museum - (from the left) Surya, Chandra, Mangala, Budha, Brihaspati, Shukra, Shani, Rahu, Ketu

Surya

Surya (Devanagari: सूर्य, sūrya) is the chief, the solar deity, one of the Adityas, son of Kasyapa and one of his wife Aditi, of Indra, or of Dyaus Pitar (depending by the versions). He has hair and arms of gold. His chariot is pulled by seven horses, which represent the seven chakras. He presides as "Ravi" over "Ravi-war" or Sunday.

In Hindu religious literature, Surya is notably mentioned as the visible form of God that one can see every day. Furthermore, Shaivites and Vaishnavas often regard Surya as an aspect of Shiva and Vishnu, respectively. For example, the sun is called Surya Narayana by Vaishnavas. In Shaivite theology, Surya is said to be one of eight forms of Shiva, named the Astamurti.

He is said to be of Sattva Guna and represents the Soul,the King, highly placed persons or Father.

 Chandra

Chandra (Devanagari: चंद्र ) is a lunar deity. Chandra (moon) is also known as Soma and identified with the Vedic Lunar deity Soma. He is described as young, beautiful, fair; two-armed and having in his hands a club and a lotus. He rides his chariot (the moon) across the sky every night, pulled by ten white horses or an antelope. He is connected with dew, and as such, is one of the gods of fertility. He is also called Nishadipati (Nisha=night; Adipathi=Lord) and Kshuparaka (one who illuminates the night). He as Soma, presides over Somvarm or Monday. He is of Sattva Guna and represents the Mind, the Queen or Mother.

He is married to daughters of Daksha Prajapathi. He has therefore 27 wives, representing twenty seven Nakshatras (constellations). Budha (the planet Mercury) was born to Soma and Taraka.

Mangala

Mangala (Devanagari: मंगल) is the god of Mars, the red planet. Mars is also called Angaraka ('one who is red in colour') or Bhauma ('son of Bhumi') in Sanskrit. He is the god of war and is celibate. He is considered the son of Prithvi or Bhumi, the Earth Goddess. He is the owner of the Aries and Scorpio signs, and a teacher of the occult sciences (Ruchaka Mahapurusha Yoga). He is of Tamas Guna in nature and represents Energetic action, confidence and ego.

He is painted red or flame colour, four-armed, carrying a trident, club, lotus and a spear. His Vahana (mount) is a ram. He presides over 'Mangal-war' or Tuesday.

 Budha

Budha (Devanagari: बुध ) is the god of the planet Mercury and the son of Chandra (the moon) with Tara (Taraka). He is also the god of merchandize and protector of Merchants. He is of Rajas Guna and represents Communication.

He is represented as being mild, eloquent and of greenish colour. He is represented holding a scimitar, a club and a shield, riding a winged lion in Ramghur temple. In other illustrations , he holds a sceptre and lotus and rides a carpet or an eagle or a chariot drawn by lions..

Budha presides over 'Budh-war' or Wednesday. In modern Hindi, Telugu, Bengali, Marathi,Kannada and Gujarati, Wednesday is called Budhvara; in Tamil and Malayalam it is Budhan.

Brihaspati

Brihaspati(Devanagari: बृहस्पति ) is the name of a Vedic deity, personification of piety and religion, the chief offerer of prayers and sacrifices, represented as the Purohita of the gods with whom he intercedes for men. He is the Lord of planet Jupiter. He is of Sattva Guna and represents knowledge and teaching.

According to Hindu scriptures, he is the guru of the Devas and the arch-nemesis of Shukracharya, the guru of the Danavas. He is also known Guru, the god of wisdom and eloquence, to whom various works are ascribed, such as the "atheistic" Barhaspatya sutras.

He is described of yellow or golden colour and holding a stick, a lotus and his beads. He presides over 'Guru-war' or Thursday.

 Shukra

Represents planet Venus.

Shukra (Devanagari: शुक्र ), the Sanskrit for "clear, pure" or "brightness, clearness", is the name the son of Bhrigu and Ushana, and preceptor of the Daityas, and the guru of the Asuras, identified with the planet Venus (with honorific, शुक्राचार्य Shukracharya). He presides over 'Shukra-war' or Friday. He is Rajas in nature and represents wealth, pleasure and reproduction.

He is of white complexion, middle-aged and of agreeable countenance. He is described variously mounted, on a camel or a horse or a crocodile. He holds a stick, beads and a lotus and sometimes a bow and arrow.

In Astrology, there is a dasha or planetary period known as Shukra Dasha which remains active in a person's horoscope for 20 years. This dasha is believed to give more wealth, fortune and luxury to one's living if a person has Shukra positioned well in his horoscope as well as Shukra being an important benefic planet in his/her horoscope.

 Shani

Shani (Devanagari: शनि, Śani) is one of the nine primary celestial beings in Hindu astrology (that is, Vedic astrology). Shani is embodied in the planet Saturn. Shani is the Lord of Saturday. He is Tamas in nature and represents learning the hard way, Career and Longevity.

The origin of word Shani(शनि) comes from the following: Shanaye Kramati Sa: (शनये क्रमति सः) i.e. the one who moves slowly. Saturn takes about 30 years to revolve around the Sun, thus it moves slowly compared to other planets, thus the Sanskrit name शनि. Shani is actually a demi-god and is a son of Surya (the Hindu Sun God) and his wife Chhaya. It is said that when he opened his eyes as a baby for the very first time, the sun went into an eclipse, which clearly denotes the impact of Shani on astrological charts (horoscope).

He is depicted dark in colour, clothed in black; holding a sword, arrows and two daggers and variously mounted on a black crow or a raven. He is depicted at other times as ugly, old, lame and having long hair, teeth and nails. He presides over 'Shani-war' or Saturday.

Rahu

Rahu(Devanagari: राहु ) is God of the Ascending / North lunar node. Rahu is the Head of Demon Snake that swallows the sun or the moon causing eclipses according to Hindu scriptures. He is depicted in art as a dragon with no body riding a chariot drawn by eight black horses. He is an Tamas Asura who does his best to plunge any area of one's life he controls into chaos. The rahu kala is considered inauspicious.

According to legend, during the Samudra manthan, the asura Rahu drank some of the divine nectar. But before the nectar could pass his throat, Mohini (the female avatar of Vishnu) cut off his head. The head, however, remained immortal and is called Rahu , while the rest of the body became Ketu. It is believed that this immortal head occasionally swallows the sun or the moon, causing eclipses. Then, the sun or moon passes through the opening at the neck, ending the eclipse.

 Ketu

Ketu (Devanagari: केतु) is the Lord of Descending/South lunar node. Ketu is generally referred to as a "shadow" planet. He is considered as Tail of the Demon Snake. It is believed to have a tremendous impact on human lives and also the whole creation. In some special circumstances it helps someone achieve the zenith of fame. He is Tamas in nature and represents supernatural influences.

Astronomically, Ketu and Rahu denote the points of intersection of the paths of the Sun and the Moon as they move on the celestial sphere. Therefore, Rahu and Ketu are respectively called the north and the south lunar nodes. The fact that eclipses occur when Sun and Moon are at one of these points gives rise to the story of the swallowing of the Sun and the Moon.

 Associated characters

Each of the graha has associations with various characters, such as colors, metals, etc. The following table gives the most important associations:

Navagraha Positioning in Hindu Customs.

As per Hindu customs, the nine Navagrahas are placed in a single square with the Sun (Surya) in the center and none of the deities facing each other.