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 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 most 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.
The name 'ruby' is used for red corundum which is colored by chromium.
Ruby comes from the latin word for red: 'ruber'. The medieval Latin adjective 'rubinus' was derived from 'ruber' and eventually started to be used as a noun for red corundum. From there it was a small step from rubinus to ruby.
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.
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.
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'.
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.
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
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  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.
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.
of azurite-malachite, which is a naturally-occurring mixture of the
vivid royal-blue, or "azure" mineral known as azurite (chessylite),
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.