Emerald

 

The name is of ancient origin. The Latin smaragdus appears, in fact, to have referred to the stone we call em ald, which is now considered as a distinct species. I: basically the green variety of beryl, although not all gr quality green beryls are called emeralds: yellow-gra stones are called heliodors; soft blue-green or even F green specimens (their color due to iron, not chromium in emerald) are called aquamarines.

Appearance The typical color is a beautiful, distince hue known, in fact, as emerald green and is due to tra of chromium in the crystal structure. But emeralds car light or dark green, bright green or leaf green. The vitrc luster is not outstanding, and is strongest in mediumstones with few inclusions. All emerald contains Inclusi although in the best quality stones, these are very faint not visible to the naked eye. They show up under a ' 20x, or 40x lens. The most common shape for gems > step or trap cut, which is also known as the emeralr. They are occasionally given a mixed, oval cut, whil: tique stones are found with hexagonal, step cuts.


chon cuts, or pear shapes with a hole in them, often used as pendants.
Distinctive features The typical emerald color is virtually unmistakable. It is only equalled by some very rare specimens of jadeite jade, which, however, is less transparent and has different physical properties. To the initiated, the inclusions in emerald can be highly distinctive: a bubble of gas in a liquid (like a spirit level), within spindle-shaped or, more rarely, truncated prismatic cavities; birefringent, circular plates of mica; multifaceted pyrite crystals or calcite rhombohedra. However, a microscope is almost always needed to recognize them. Although not the typical emerald color, some green tourmalines may look similar, but they can be distinguished either by their marked pleochroism, or by the fact that tourmalines which are given an emerald cut display alternating, longitudinal lines of lighter or darker color, when viewed through the table facet. Olivine may also be a verdant green color vaguely similar to that of some atypical emeralds; but the powerfui birefringence of olivine is detectable with a simple lens, a double image of the opposite facet edges being clearly visible in certain directions through the table facet. In an> case, the density of either tourmaline or olivine immediately distinguishes the stone from emerald.

Occurrence The biggest and most beautiful emeralds come from the famous Chivor and Muzo mines of Colombia. Much smaller quantities of emeralds, mostly of medium-light color, come from Brazil, and small, very intensely colored stones, characterized by numerous minute inclusions of molybdenite with a metallic appearance are found in the Transvaal.

In the last few decades, increasing quantities of emeralds have been found in a series of small deposits in Eas' Africa-principally in Zimbabwe, Zambia, and Tanzania These are quite a strong color, sometimes with a bluishgreen tinge; and they often contain mica plates and, sometimes, thin crystal needles. The most famous of these emeralds are the ones from Sandawana in Zimbabwe, which are valued for their color. Emeralds with similar characteristics also come from the mountains of India and Pakistan as well as the Soviet Union (Urals), and formerly Austria Value Stones of fine color, weighing more than 2 carats are among the most highly valued gemstones, and their price may equal or exceed that of diamonds. Less ideally colored varieties-too dark or too pale are worth quite a lot less; and if they are slightly turbid as well, the value i< reduced even further.

Simulants and synthetics The Romans are known tc have imitated emerald with skilfully worked green glass Glass was also used in later centuries, extraneou~ particles sometimes being incorpoeated to simulate inclusions.

Doublets have also been used as imitations, with a lowe portion of green glass and a top portion of garnet, or triF lets, with a layer of colored cement sandwiched betweer two layers of colorless beryl, synthetic spinel, or quartz Synthetic emeralds have likewise been widely produce over the last few decades. Generally of good color, these are mainly distinguished from the natural variety by the inclusions and other growth features. There are a lot of these synthetic stones about, but their cost is quite high, so that the market for them is saturated.

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