A brief historical evaluation of precious and semi-precious gems

The line between what constitutes a "precious" or "semiprecious" gemstone has more to do with historical context than any objective measure of its current value. Historically, the so-called "precious" or "cardinal gems" included diamond, emerald, ruby and sapphire, but also included amethyst which today is both abundant, and inexpensive.

Other than the historic, ceremonial, or religious significance of labelling a gem as "precious," or "semiprecious," there is no actual difference between these designations, and their use can be misleading, inappropriate, and inaccurate. In fact, some of the stones in this category might very well be considered "precious," due to their increasing scarcity, high price, or changing consumer tastes. Therefore, inclusion or omission of a particular gemstone/mineral in the "precious" or "semiprecious" category should neither diminish, nor enhance a stone's prestige or monetary value.

Diamond

Diamond is a gemstone composed of chemically pure carbon, with a cubic crystal structure and manifesting extreme hardness resulting from the incredibly strong chemical bonds between the carbon atoms. Diamonds are valued for their brilliance, fire and beauty. Usually perceived to be a colorless gemstone, diamondsactually occur in every color including: yellow, green, pink, blue, purple and red. Diamond color and clarity can be altered such treatments as irradiation, heat and high pressure.

The value of a diamond is set by measuring and evaluating what in the diamond business is referred to as the four C's. - color, clarity, carat weight and cut. Diamond color is measured on a scale ranging from D to Z with D being the most colorless (and mosthttp://www.langantiques.com/university/images/3/36/Diamond.jpg desirable). Clarity has a series of designations that range from Flawless to Included representing the relative number, type and visibility of inclusions. Carat is a measure of weight where one carat is equivalent to 1/5 of a gram or 200 milligrams. Cut includes the shape of the finished diamond as well as a determination of how well the diamond was fashioned, its proportions and finishing details.


For over 2,500 years the only known source for diamonds was the Golconda region in India. After the depletion of the diamond mines in India c. 1700s, a new diamond deposit was discovered in Brazil c.1725. Brazil quickly became largest supplier of diamonds worldwide and remained so until the discovery of diamonds in South Africa in 1866. De Beer's Consolidated Mines LTD was formed in 1888 to stabilize the South African diamond market and maintained a near monopoly on the diamond trade for over 100 years, controlling 80% of the market. Today their market share is less than 50%.


Diamond is the birthstone for the month April and commemorates the 10th and 60th anniversary (65th in some countries.)

Ruby

The name 'ruby' is used for red corundum which is colored by chromium.

Etymology

Ruby comes from the latin word for red: 'ruber'. The medieval Latin adjective 'rubinus' was derived from 'ruber' andhttp://www.langantiques.com/university/images/f/fd/Tiffany_Ruby_Ring.jpg eventually started to be used as a noun for red corundum. From there it was a small step from rubinus to ruby.

History

Ancient History

The area around Mogok, Myanmar has seen human habitation since the middle paleolithic period. It is not so hard to believe that these early inhabitants would have stumbled upon the fine rubies of this locality and kept them as decoration, amulets or maybe even tools. Archaeological investigations have been very scarce. The restrictions for foreigners to enter the country that have been put in place by the military regime of Myanmar prevents us from getting a clear picture of the ancient inhabitants of the area and their use of rubies. Another ancient source of gem corundum has been Sri Lanka.


We can find written accounts of red stones that could be ruby in the writings of Theophrastus who speaks of red stones that resemble a hot coal when viewed with the sun behind it. He calls this stone anthrax but whether he was describing garnet, spinel or ruby isn't clear. Pliny's account on red stones is similarly vague and seems to describe more than one red gemstone under the same name; carbunculus. An interesting note is that Pliny mentions glass imitation stones that can be distinguished from genuine gemstones by hardness and inclusion studies.

 

Saphire

Sapphire is the term used for all colors of the gem quality mineral corundum, with red as the only exception (the red variety of corundum is called ruby.) The term sapphire, without color prefix, refers solely to blue stones. Until recently, other fancy colored sapphires bore names such as 'oriental topaz' (yellow), 'oriental emerald' (green) and other misleading monikers. Today these other colored corundum are referenced as sapphires with a color prefix, e.g. purple sapphire, orange sapphire and so on, in order that there is no confusion to their identity.

Etymology

The word sapphire can be found in the Old French word safir which in its turn is likely to have come from the Latin word sapphirus and the ancient Greek sáppheiros. The Greeks also seem to have used the word to refer to another blue stone: lapis lazuli. Hebrew knows the word sappir, meaning 'the perfect'. It has been suggested that in old Arabic sapphire was called sappeer (to scratch). Another possible origin of the word is the Sanskrit word sanipriya that indicated 'a dark colored stone sacred to Saturn'.

Emerald

This illustrious and most esteemed member of the beryl family has long been regarded as one of the most precious of all gemstones, surpassed only by ruby. Cellini in the 16th century remarked that the value of a fine emerald would be half the price of a like ruby, but was four times more valuable than diamond.

The color of emerald, the birthstone for the month of May, has been described as the "warm green of a meadow in spring". Its grass green primary hue is usually modified by slight bluish or yellowish undertones. A vivid, slightly bluish green is the most desirable color. The most valuable emeralds are top quality stones from Colombia, unrivaled in their - chromium induced - silky hue of green.

Emerald is a type III gemstone on the GIA clarity scale as they are usually quite included. The vast majority of emeralds have been treated to improve their clarity and appearance, a practice that has been widely accepted for centuries. Cedar oil, a natural and colorless oil with a refractive index similar to emerald, is the most common and accepted method of treatment, providing a stable and reversible effect.

Agate

Source: Occurring worldwide

Agate is a fibrous, translucent to opaque, compact microcrystalline variety of chalcedony (quartz) that occurs in banded white, gray, brown, grayish-green and grayish-blue hues. Agates are formed by silica-rich water percolating through cavities and fissures in volcanic rock, and occur worldwide. Agate is a relatively porous material that is easily dyed to alter or enhance the color. Fibre

 

Apatite

Source: Brazil, Canada, Colombia, Germany, Madagascar, Mexico, Russia, Sri Lanka, USA

Apatite is not a single mineral, but a phosphate mineral group consisting of chlorapatite, fluorapatite, and hydroxylapatite. Each individual mineral has a certain level of chlorine, fluorine, or hydroxy in varying amounts and combinations. The most common gem variety is a translucent to transparent semiprecious gemstone that is steadily increasing in popularity within the jewellery trade, and its greenish-blue 'seawater' colour makes it an inexpensive, although somewhat soft substitute for aquamarine.

 

Almandine Garnet(Ceylon Ruby)

Source: Australia, Burma, East Africa, Sri Lanka, USA (Alaska, New York)

The name "almandine" was derived from alabandicus; a name coined by Pliny the Elder [3] to lesser carbuncle gemstones discovered at Alabanda, in Asia Minor. Almandine garnet is sometimes mistakenly referred to as "almandite."

Almandine belongs to the "garnet group" of minerals commonly found within metamorphic rock and associated with ultramafic igneous rock formations. Garnet is classified as a nesosilicate in the Silicate mineral group. There are six common varieties of garnet that are identified by their chemical composition and color. They are almandine, andradite, grossularite (tsavorite), pyrope, spessartite, and uvarovite. Almandine is an iron alumina (iron aluminum silicate) garnet variety, and when the iron is substituted with magnesium it becomes the magnesium aluminum garnet, pyrope. Almandine is commonly found embedded in, or associated with mica-schist or gneiss. The color of almandine garnet tends to be redish-orange, reddish brown, brownish-red, deep-red, or purplish-red. Purplish-violet varieties are sometimes referred to as "Syriam garnet," or "Pegu garnet," named after Syriam, a capital of the ancient kingdom of Pegu (Bago), in Lower Burma. Syriam garnet may also be referred to as "amethystine or oriental garnet.

 

Aventurine Source: Chile, India, Spain, Russia, USA

Aventurine quartzite is a translucent to opaque, green to bluish-green tectosilicate rock that is a variety of quartz. Aventurine's characteristic glistening or shimmering effect is known as "aventurescence," which is the result of uniformly oriented, platy mineral inclusions within the rock matrix. The name "aventurine" is derived from the Italian name "a ventura" or "by chance."

The presence of fuchsite inclusions, a chrome-bearing variety of muscovite mica, gives aventurine its characteristic silvery greenish-blue sheen. High quantities of fuchsite can cause aventurine to be totally opaque. This macrocrystalline quartz has a massive crystal habit, which is an aggregate of interlocking quartz grains.

Azurite-Malachite Specimen of azurite-malachite, which is a naturally-occurring mixture of the vivid royal-blue, or "azure" mineral known as azurite (chessylite), and bright-green malachite. Azurite and malachite are combined in a geological process known as syngenesis.

zurite-malachite is typically found within copper deposits of the desert southwest United States, primarily in Arizona. Azurite is a hydroxide-containing member of the copper carbonate class of mineral, which has a massive, nodular or tabular habit, often occurring in stalactitic form with prismatic crystals.

Azurite has been used as a blue pigment for centuries, and the name "azurite" was derived from the Arabic word azul, meaning "blue," and the Persian word lajhvard, meaning "blue stone," or "stone of azure." Azurite-Malachite is also found in Africa, Australia, Chile and France.