HomeIntroduction to Gemology

1       Scientific perspective

1.1     Definition of Gemmology

Gemmology

  • GIA #1
    • Derived from the Latin word “gemma” – gem & Greek word “logos” – discourse, word or speech
    • Spelt with one ‘m’ in USA & two ‘m’s in Britain
    • A branch of mineralogy
  • Read
    • It is a distinct science, concerned with the technical aspects of gems and gem materials
    • First gemstone book appeared as early as 1652
    • But only in the last half of the 19th century that the study of gemmology began to emerge as a specialized offshoot of an established branch of Science – Mineralogy
  • GIA #1
    • But since Mineralogy is concerned with many other subjects and does not cover many of the matters of interest in Gemmology, it ought to be considered a distinct Science
    • Gemmology is also concerned with gemological testing methods, cutting & finishing, synthetically manufactured gems, precious metals, their alloys as well as appraising procedures
    • Also covers organic materials like pearls, that is not dealt with in mineralogy
  • Hughes
    • Gemmology is also a knowledge of a certain type of merchandise, like watches, stamp collecting etc
    • It is also a rich tapestry of interwoven disciplines – not just mineralogy, physics, chemistry, crystallography and geology, but also, history, trade, economics, decorative arts, religion, mysticism and magic.
  • Emporia
    • Gemmology is the distinct science of gems, most closely related to mineralogy, which is a branch of the geosciences that draws from chemistry, physics, and geology. Physics and chemistry help to relate the physical, chemical, and optical properties of minerals; geology creates the understanding of how the gem material formed and where to prospect. Gemmology is not only concerned with the study of gem materials, but also gem testing and evaluation methods, cutting and polishing, synthetically manufactured gems, precious metals and alloys, grading, marketing, and sales.

1.2     Definition of a gem

  • Gem/Gem material: any material which is used for adornment or decoration, and has particular attributes or value factors
  • Unfashioned material that is worth processing into a gem or ornament is termed ‘rough’
  • Emporia

Gemstone is a collective term for all objects used with ornamental stones for personal adornment that possesses beauty, durability, and stability. Beauty, a quality that varies among individuals, can be based on one or any combination of: colour or lack of colour, lustre, transparency, or enhanced optical properties due to cutting and fashioning by the lapidary. Durability is the resistance of the gemstone damage and dependent upon physical properties, such as hardness and tenacity. Tenacity is the resistance to bending and breaking, while hardness measures the resistance to scratch. Diamond cannot be scratched by any other mineral and therefore, it is a gem with high hardness; diamond has low tenacity, in part due to perfect cleavage. Nephrite jade is relatively soft for a gem, easily scratched by dust in the air, but it is composed of fibrous crystals that resist breaking and therefore, it is tough or has high tenacity. Stability refers to the gem's ability to retain colour in spite of heat, light, or chemical assaults.

Of the 4,000+ known minerals, 70 possess qualifications for gemstones, but of these, only approximately 20 are commonly encountered[i]. These minerals include: diamond, corundum (ruby, sapphire, star ruby and sapphire), beryl (emerald, aquamarine, morganite, goshenite, golden or heliodor), chrysoberyl (cat's eye & alexandrite), spinel, topaz, zircon, tourmaline (indicolite, rubellite, schorl, elbaite), garnet group (almandite/almandine, rhodolite, pyrope, grossular/tsavorite, spessartine, uvarovite), quartz: crystalline (rock crystal, amethyst, citrine, cairngorm or smoky, rose, aventurine, tiger's-eye, rutilated), quartz: cryptocrystalline (chrysoprase, carnelian, sard, bloodstone, agate, onyx, jasper, agatized or petrified wood), olivine peridot (chrysolite), jadeite jade, tremolite-actinolite or nephrite jade, spodumene (kunzite, hiddenite), feldspar group (microcline amazonite, labradorite, orthoclase moonstone, oligoclase sunstone), turquoise, lapis-lazuli, and opal.

(Berkeley)A gem is a naturally occurring material desirable for its beauty, valuable in its rarity, and sufficiently durable to give lasting pleasure.

·       It should be naturally occurring, but it need not be crystalline.

·       Beauty is determined by brilliance, iridescence, color, sparkle, and play of color.

·       A gem should be durable against heat and common household chemicals.  It should not be easily scratched or broken.  Brittleness is a measure of the gem's tendency to crack or cleave.

1.3     Gemstones, their value and influence

Most gems are minerals and thus, the history of gems is tied closely to history of minerals. Minerals and rocks are the foundation that all present day civilization is based upon. Early humankind created tools from quartz and flint or chert. As the Stone Age progressed into the Bronze Age, metallic minerals were sought after for a variety of uses from weapons to hinges. Gemstones, or material without a utilitarian value, were luxury items and appreciated for their beauty, much the same as today.

In addition to personal adornment, gems have always been regarded as somewhat mysterious. They have been used as primitive medicines and have been quite important as amulets and talismans. Paintings in Egyptian tombs some 5,000 years ago depict the smelting of ores from metals, weighing gems, and fashioning lapis and malachite. Crushed malachite was used as a pigment for painting, as well as eye make-up for ancient Egyptians, which is created by mixing ground malachite with ants! More than 4,000 years ago, Egyptians created jewelry by stringing cylindrical beads together into a wide fan-shaped necklace called bead collars. The beads were blue faience (pronounced fay aunts; and it is glazed clay), turquoise, gold, lapis lazuli, and carnelian. The beads would eventually be polished and inscribed with symbolic markings, used to ward off evil spirits. Carving gems developed over the years and beetle images, called scarabs, were common in the 9th Egyptian dynasty, around 2050 B.C.

Even earlier Greek and Roman civilizations were using minerals as gems and the art of carving rocks and minerals was perfected. The early gems were used for personal adornment, the same as today; but, usually the importance to the wearer was greater than today because ancients believed the gems held magical powers, lucky talisman, amulet, or fetish.

Virtues were assigned to gems. Reddish brown carnelian was one of the luckiest jewels to wear. "No man who wore a carnelian was ever found in a collapsed house or beneath a fallen wall" and thus it was a talisman of good luck and joy for ancient Babylonians and Greeks (Kunz, 1971, p. 65).

Early Christian theologians believed gazing at blue sapphire would elevate one's thoughts from earthly to heavenly matters and in the 6th century it became a ruling that every cardinal wear a sapphire ring on his right hand. Sapphire is a variety of the mineral corundum. The red version of corundum, ruby, according to Burmese legend was hatched from eggs laid deep in Earth, and has always been prized for it's red color which could shine through the thickest of layers of clothing (Harvey, 1981, p. 9). Ruby was believed to protect your house and land from storms and lightning and a woman wishing to prove her virtue should wear the ruby on her left hand as there it would control amorous desire (Harvey, 1981, p. 9).

Garnets endow the wearer the ability to make deep and lasting friendships. They were used as bullets by some tribes, some 400 years ago, because ..."the blood-red stones would inflict a far more grievous wound on their enemies than the common lead bullet" (Harvey, 1981, p. 11).

The green emerald was often associated with Venus, the earth-goddess, and was thought to be a sacred symbol of fertility and growth. Although some believed it to be a symbol of fertility, it may have been one of the earliest forms of birth control as it was also said a woman should not wear an emerald until she was fifty!

Chrysolite, or better known today as peridot or olivine, was first mined by Egyptians on the island of Zeberged in the Red Sea area. A favorite of the Pharaohs, peridot had the power to dispel dark forces. (Wasn't that the colour of the light saber for Jedi knights in the Star Wars saga?!).

Ancient Babylonians carved symbols in bloodstone, or heliotrope (turn to the sun), which allowed the future to be foretold. Later it would become a Christian symbol, the red spots representing the blood of Christ diffusing in the green stone. In the sixteenth century it had the ability to cure nosebleeds or when placed on any wound, stop the bleeding.

Agates, a gem frequently formed in the vugs of volcanic rocks, sometimes have a circular, wavy or zigzag pattern that can resemble the shape of an eye; when in this shape, it was used as a amulet to guard against the evil eye or as an eye of an idol (Harvey, 1981, p. 19).

From ancient times, purple has always been a color associated with nobility. At times, amethyst, the purple variety of quartz, has been held in the same value as diamond. It can be found among crown jewels and in the rings of religious leaders. Amethyst actually means "not drunken" and of course, would protect the wearer from drunkenness.

Beryl was the gem connected to the biblical tribe of Gad, the tribe of good fortune. It was associated with fortune telling and many women in ancient times gazed into a bluish-green beryl sphere to foretell the future.

Not all gems were lucky though. Onyx, the stone of sadness, was dreaded by ancient Chinese. It was believed that even entering a mine where it could be found would lead to terrifying dreams, doubts, and disputes (Harvey, 1981, p. 7). Topaz is believed to be influenced by the Moon and therefore it shines most brightly at night. Topaz has special powers transmitted to the wearer; long life, beauty and intelligence will wax and wane with the phases of the Moon.

Even gem dreams had great significance. Carnelian dreams could bring misfortune; moonstone dreams could mean danger; dreaming of jet predicted sorrow. For friendship, safety, hope and prosperity, one should dream of pearls (a symbol of purity), amethysts, emeralds, and turquoise. Now there's something to think about before bed tonite!

1.4     Appreciation of the rarity of gems

How rare is rare?

  • Typically, a diamond deposit yields about 5g gem/1000kg of mined material.  That's 5g per million grams!


2       Basic qualities of a Gem – Value Factors

Factors other than beauty, durability, and stability, that affect the value of a gemstone include: rarity, demand or fad, and portability. The rare gem, or one with limited available quantities, is considered desirable by those who can possess it. Rarity can lead to increased demand and prices, which can lead to new discoveries that will bring down the price. Demand and gem value fluctuate with current fads or fashion. Dark red garnets from Bohemia were very popular in the nineteenth century, but these jewelry pieces are not in demand today. Amber and turquoise jewelry was popular at the beginning of the twentieth century, fell out of favor, and has experienced a resurgance of popularity at the end of this century. Lastly, gemstones are valued for their portability, which necessitates a small volume, high value commodity.(Emporia)

2.1     Beauty

  • The most obvious of qualities Read
  • GIA #1
    • Cannot be easily quantified, depends on subjective factors to do with appearance
    • Unless a gem material possess or possess potential beauty, it cannot be considered or to qualify as a gem or gem material

·  Transparent minerals: The brightness, dispersion (fire) the transparency (purity) intensity of the colour (for the coloured stones). These are determined by the cut of the stone.

·  Translucent minerals: Colour or the reflection, opalescence, the changing luster or asterism (in the case of the phenomenal stones)

·  Opaque minerals: Purity and intensity of the colour, the propensity with reflecting their colour well and taking the polish. All these factors of beauty are highlighted by the size and polishing.

 

2.2     Rarity

  • A quality that must be present in some degree in all gems worthy of the accreditation
  • Frequently plays an important role in determining the value of the gem ( the rarer the material in great demand as a gem, the higher the value). That is to say, the rarity of a gem is also a function of supply and demand, fashion and scarcity of source; unlike the previous mentioned quality(beauty) of a gem
  • Unusual properties gems contribute to its rarity( chrysoberyl cat’s eyes, alexandrite)
  • Control on supply pipe line also affects rarity ( value of diamonds is affected by De Beers’ control)
  • YET
    • Gem/gem material may sometimes be too rare to create a demand (eg. Benitoite, euclase). The rarity is such that it generates insufficient awareness amongst people, and therefore the market generates too little demand to elevate the gem/gem material to sufficient status to fetch high prices

2.3     Durability

  • To be of use as a personal ornament, the gem must be able to resist ordinary wear sufficiently well to retain its luster and polish as well as to stay intact and resist damage (i.e. beauty is lasting when given reasonable care.)
  • Practical quality as a gem would not be able to survive day-to-day wear and tear or chemical attack, and thus losing its surface polish

2.3.1    Factors affecting durability

2.3.1.1   Hardness

  • Ability to resist scratch

2.3.1.2   Toughness

  • Ability to resist cracking chipping and actually breaking

2.3.1.3   Stability

  • Ability to resist chemical attacks like oxidation and the ability to not disintegrate over time

2.4     Acceptability

2.4.1    Demand

“The fourth factor having a bearing on the value of gemstones is DEMAND, or VOGUE. There are times when some of the less important gemstones enjoy great demand and other times when they are in relative eclipse. In the twenties, for example, amber was highly promted and a great demand for it was created. It soon represented the second most important gem importation into this country in terms of gross value. The fad did not last long, however, and at the present time amber is rarely seen in jewellery stores.” GIA Assignment #1

2.4.2    Tradition

“One of the most important factors affecting the demand and value of gemstones is tradition. It might be said that tradition, as applied to gems, is the sum total of all the effort throughout the centuries to interest and educate the public in the use of gems for ornamentation, symbolism, and as a medium of exchange. Such effort includes the deliberate promotions on the part of jewelers, the publicized purchases and subsequent use of gems by royalty and wealthy individuals, the use of gems for symbolization in various churches and other developments in which gems play a part. All of these activities have, over a period of time, created an acknowledgement by the public of the importance of gems.

 

Demand follows acknowledgement and is spurred on by rarity. It is human nature to want the things we cannot have or those that are difficult to obtain, particularly if ownership gains recognition of achievement. If beauty alone were the only sought-for quality in jewellery and gems, then imitations, synthetics and plated metals would constitute the jewellery industry. There would be little reason for anyone to go to the effort and expense of searching out the comparatively small number of natural gems available for resale to the public. On the contrary, tradition has established the importance of the principal natural gems and has associated them with genuine achievement in the church, business, family and other groups and associations. Achievement of any kind has in itself an element of rarity, and thus it is effectively symbolized by the rare. In view of this, man-made synthetics and imitations will never take the place of the natural stone, no matter how beautiful they are, other than for those who cannot pay the price of the natural. Even here they are only accepted as a substitute and, as such , are valued only at production plus handling costs.”

2.4.3    Portability

“Another factor contributing to the importance of gems is PORTABILITY. This applies to any fine gemstones because it represents a high concentration of value in a small object, permitting the owner to transport great wealth effectively on his person. This is what gives gemstones a universal security value, perhaps greater than any other known commodity. This is the factor that influences royalty and many wealthy families to invest a certain amount of their funds in jewels. When everything else fails, even their government, they can take or send their gems out of the country and realize a return on them quickly. This has always been a factor of great importance in Europe. General insecurity in recent times has given weight to the portability of gemstones as a factor in the consideration of their purchase.”


3       Weights and Measures

3.1     Carat

  • FGA
    • Derived from the name of ‘carob’ or locust tree(Ceratonia siliqua)
    • Or from the seed ‘kuara’ of the African coraltree [Schumann]
    • Dried carob seeds were used by traders as the unit for mass due to their remarkably consistent mass of around 0.02g
    • Carat is denoted by ‘ct’
    • A carat is a fifth of a gram (defined in ?? year) ie 1 ct = 0.02g, or 5ct = 1g

3.2     Point

  • For intermediate mass determination
  • Each carat is divided into 100 points. I.e. 1ct = 100pt
  • Denoted by ‘pt’
  • Largely used for weighing small diamonds

3.3     Gram

  • Mass measure used in the trade for less precious gems, and especially gem roughs

3.4     Grain

  • Formerly the measure of mass for pearls
  • It is a quarter of a carat. Ie 1 grain = 0.25 ct or 1ct = 4 grain
  • Increasingly substituted by the use of carat

3.5     Momme

  • Old Japanese measure for cultured pearls
  • Hardly used anymore except by wholesale distributors
  • 1 momme =  3.75g =18.75 ct

 


4       Classification of Gemstones

Of the some 3000 minerals that have been identified, only about 90 varieties that produce specimens possessing the requisite beauty and durability to be considered gemstones. Of the 90, only about 20 are particularly important to the gem trade.

 

(Emporia) Two traditional modifiers of gemstones, precious and semi-precious, are mostly discouraged from usage today as they imply one is more beautiful and valuable than another. In part, these designations began as a result of taxation on imported goods, where the highest taxes were paid on diamond, ruby, sapphire, and emerald, and other gems were taxed at a lower rate. Schumann (1997) stated the semi-precious stone designation was derogatory, or believed to denote a gem of lesser value and hardness, but he promoted the term, colored precious stone, as a new trade term used to include all colored and noncolored gems except for diamond (p. 10). All material that fits the definition is referred to as gemstones or gems and subdivided into diamonds and colored stones or colored precious stones.

4.1     Scientific Classification

Since most gemstones are minerals, the classification method used in gemology is the same one applied by mineralogists to the various minerals, with minor adjustments. Each mineral that produces gemstones is considered a gem species. A gem species is characterized by a definite chemical composition and usually a characteristic crystal structure. Therefore, each species possesses its own characteristic properties. However, most species include a number of different types of material with variations that are usually based on colour and transparency; each of these is called a variety.

 

For example, ruby and sapphire are both varieties of the gem species corundum. Ruby is the red variety and sapphire is the name applied to blue and all other colours. Since both are corundum, ruby and sapphire have the same chemical composition, the same crystal structure, and the same properties. They differ in only colour. By the same token, emerald and aquamarine are varieties of the gem species beryl.

 

There is one other classification of importance to gem materials: the group. A group is a number of closely related species. There are two groups of importance in the study of coloured stones. The first is garnet. It is composed of a number of minerals having the same crystal structure but with variations in chemical composition. Thus the garnet group has a number of closely related species. The second is the feldspar group, which includes amazonite and moonstone as varieties of different species.

 

The jades, the two important species of which are jadeite and nephrite, are not members of the same group, although they are often treated as a group by gemologists because of their similar characteristics. The more important gem materials and their principal varieties are listed on the accompanying table.

4.2     Commercial Classification

 

Gems may be described as those specimens of minerals and organic materials used for personal adornment that possess beauty, rarity and durability. The organic materials used as gems are pearl, coral, amber, jet etc. The subject of gemstones is divided into two classifications: diamonds and coloured stones. The term coloured stones is used in the jewellery industry and refers in its broadest sense to all gem minerals plus organic gem materials, but does not include diamonds. In a narrower sense, pearls are also eliminated from this classification and treated separately; however, they will be studied with coloured stones in this course.

 

Diamonds has never been considered in the same category as coloured stones for several reasons: 1. In this finer qualities it is usually nearly colourless, whereas the finer qualities in the major varieties of the other gem minerals are coloured; 2. the physical and optical properties are sufficiently different from other gems to make its beauty and subsequent use totally distinctive; 3. unlike good-quality coloured stones, diamonds have been consistently available in both quantity and quality to permit standard competition in general marketing procedures and pricing. The subsequent competition in sales has demanded a specialization that has not been required of individual coloured stone species. In other words, competitive diamond marketing is a full-time occupation. The sources of rough, the cutting techniques and marketing are totally foreign to those of coloured stones, and thus it has rarely been practical to attempt to combine the two other than at retail sales level.


5       Nomenclature of Gemstones

 

The oldest names for gemstones may be traced back to Oriental languages, to Greek and to Latin. Greek names especially have left their stamp on modern gem nomenclature. The meaning of old names is not always certain, especially where the first meaning of the word has been changed. Also, in antiquity, totally different stones were given the same name simply because they may have had the same color.

 

Original names referred to special characteristics of the stones, such as colour(for instance “prase” for its green colour), their place of discovery (“agate” for a river in Sicily), or mysterious powers (“amethyst” was thought to protect against drunkenness). Many mineral names which were later also used to name gemstones, have their origin in the miners’ language of the Middle Ages.

 

Nomenclature has been viewed scientifically only since the beginning of the modern age. Because of the discovery of many hitherto unknown minerals, new names had to be found. A principle for naming new minerals and gemstones was established which is still adhered to today. A new names is devised to refer to some special characteristic of the mineral, based on Greek or Latin, the chemical constituents, the place of occurrence, or a person’s name.

 

Through such name-giving, not only experts are honoured but also patrons or others who may or may not have any connection with mineralogy or gemology. But since everyone did not always agree when a name was given, various names for the same mineral have come into use and persist to this day.

 

The gemstone and jewellery trade added more of their own names, mainly to stimulate sales, producing a large number of synonyms and variety names for gemstones.

 

In order to correct this state of affairs, all newly discovered minerals, as well as the intended new names, must now be presented for evaluation to the Commission on New Mineral Names of the IMA(International Mineralogical Association), to which experts from all over the world belong.

 

Anyone who believes that he has found a new mineral or an important gemstone variety must have his first right and other legalities as well as the name-giving checked. Only then is the name of the mineral and/or the gemstone sanctioned and standardized.

 

Since in the gemstone trade, the danger of purposefully giving a wrong name and improper evaluation of goods is especially high, the Commission for Delivery Conditions and Quality Securing at the German Norm Commission has published in 1963/70 in the RAL A5/A5E Guidelines for Precious Stones, Gemstones, Pearls and Corals(for Germany) to protect against unfair competition.

 

Permitted definitions and the trade customs for gemstones are internationally regulated through the International Association of Jewelry, Silverwares, Diamonds, Pearls, and Stones, in short CIBJO(Confederation Internationale de la Bijouterie, Joaillerie, Orfevrerie des Diamants, Perls, et Pierres).

 

In the United States, the Federal Trade Commission (FTC) Guides for the Jewelry, Precious Metals, and Pewter Industries serve a similar purpose.

 

Certainly, the aforementioned institutions have led to better communication and to more security for the gemstone buyer and seller, but such measures, naturally, cannot ensure the enforcement of an absolute guarantee for genuineness.

 

(Emporia) Gems were named on the basis of color (prase for its green color), place of occurrence (agate for a Sicilian river), mysterious properties (amethyst believed to protect from drunkenness), a special characteristic (moonstone for a whitish-blue schiller effect), or to honor the discover or person (smithsonite for James Smithson). The gem and jewelry trade sometimes assigned names to promote sales, even if it was misleading (e.g., smoky topaz is in fact smoky quartz and not topaz). See Schumann (1997) for some common misleading names (p. 12-13). Today new gem names must be presented for evaluation by the Commission on New Mineral Names of the International Mineralogical Association (Schumann, 1997, p. 12). On an international scale, the Confederation Internationale de la Bijorterie, Joaillerie, Orfevrerie des diamants, perles, et pierres or CIBJO (International Association of Jewelry, Silverwares, Diamonds, Pearls, and Stones) oversee gem definitions and trade customs.


6       Terms Precious and Semiprecious

Perhaps the most obvious sign of a lack of appreciation of gemstones is the common use of the term “semiprecious”. While in a famous retail store an Institute staff member noticed a couple examining with obvious interest and appreciation an attractive brooch set with green stones. He over heard the man ask about the stones in the piece. The “salesman” if he could be called that, answered “Oh, those are just semiprecious stones called tourmaline”. The prospective customers, who had shown keen interest in the brooch, left the store immediately without looking at other merchandise. This example points up a practice that is all too common among jewellers.

 

Almost every gem mineral is found and is for sale in the industry in a great variety of qualities. One quality of jade in a ten carat size may sell for fifty cents and another quality for $20000 or more. A ruby may be a poor nontransparent quality and sell for several dollars per carat or it may be very fine and sell for $20000 per carat. A large opal may range in value from $5 to $5000. Almost every variety of the transparent gem species may occur in gem quality and be properly called a precious stone from a relative price standpoint, whereas another specimen of the same variety may be almost worthless. Not every ruby is precious and not every piece of jade is semiprecious. This is one reason for calling gemstones and not classifying them as precious and semiprecious. More important is the fact that the moment that we call stones semiprecious, we have lessened their value in the eyes of the general public, and the desirability and sale of many stones of great merit are thus substantially decreased.

 

The most common query received by the jeweller from the customer who sees an unfamiliar stone seem to be, “Is it a precious stone?” If the jeweller is not a student of coloured stones, his probable answer is “No, it is only a semiprecious one; diamond, ruby, sapphire and emerald(and perhaps he includes pearls) are the only precious stones.” Every experienced gem salesman knows that this statement may have the result of immediately destroying in the customer’s mind any interest whatever in the stone about which the inquiry was made and for which the inquirer may have been a customer. This is another of the reasons for the common belief that “coloured stones don’t sell”.

 

Few people desire anything but the best. They don’t have to have gems and jewellery, and unless they have a desire or a need for a thing, they won’t buy it unless high pressured. High pressure results in dissatisfied customers. Semiprecious seems second best. Therefore, the buying public, either lacking in sufficient knowledge or appreciation of these stones called semiprecious by their salesman, or unable to find them for sale by a dealer who has the knowledge and appreciation that they themselves lack, buy synthetics or glass imitations in preference to the doubtful value of a semiprecious thing. Why should we discourage sales by continuing the use of this term? It should be abandoned totally.


7       Bibliography and Supplementary Reading

Webster, Practical Gemmology, Lessons 1,2

Read, Gemmology, Chapters 1,2,3

Hurlbut, C. S., & Kammerling, R. C. (1991), Gemology, Chapters 1,2, NY: John Wiley & Sons, Inc.

Gemmological Association of Great Britain, FGA Foundation course materials, Chapters 1,2

GIA Colored Stones course materials

CGA Preliminary course materials, Chapters 1,2

Schumann, Walter. (1997) Gemstones of the World, NY: Sterling Publishing Co, Inc.

Harvey, Anne (1981). Jewels. London: Bellew & Higton Publishers Limited.

Kunz, G. F. (1971). The curious lore of precious stones. NY: Dover.

 



[i] Hurlbut & Kammerling, 1991, p. 3

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