Why are emeralds green

emerald

Author: Torsten Purle (steine-und-minerale.de) | Last update: 30.03.2021


Emerald - properties, formation and use

English: emerald | French: émeraude




Emerald - The green beryl

For a long time, all green stones were grouped under the name emerald, as the name comes from ancient Greek (smáragdos) is translated as green. Nowadays only the green variety of the beryl group is called emerald.


Table of contents emerald

Properties of emerald

Emeralds are silicate minerals with the chemical composition Al2Be3(Si6O18), which are counted among the beryls in the further subdivision. Further representatives of the beryl group are the minerals gold beryl / heliodor, aquamarine, pezzottaite, morganite, goshenite and bixbit / red beryl.

Emerald crystallizes in both the trigonal and hexagonal crystal systems and forms columnar crystals.

The luster of the green mineral is glass-like with transparent to translucent transparency. Emeralds are characterized by a shell-like, uneven break, the cleavage is imperfect.

With a Mohs hardness of 7.5 to 8 on the 10-point scale of the hardness of minerals according to the mineralogist Friedrich Mohs (1773 to 1839), emerald fulfills the criterion of gemstone hardness (= Mohs hardness over 7). The density of emerald is 2.6-2.8 g / cm3.




The color of emerald

The color of emerald is green in different intensities; are coloring Chromium and traces of iron. In rare cases, the mineral is also due Vanadium colored green.

Based on the color and the type of inclusions in the emerald - healing cracks, gases, liquids or other minerals - statements can be made about the origin of the emerald crystals.

  • Emeralds from Zimbabwe are bright green with included tremolite needles.
  • Brazilian emeralds are yellow-green and have fine inclusions of liquids and gases.
  • Mica implies that Emeralds from South Africa cloudy appear.
  • Leave minerals stored in emerald crystals Australian emeralds pale and "dirty" appear.
  • Are the most variable Emeralds from India, recognizable by their characteristic angular cavities in which gases or liquids are located. In professional circles, the inclusions in emeralds are called Jardin Gardens because the inclusions are reminiscent of trees, branches or flowers - small gardens.
  • Most sought-after at the gemstone market are emeralds from Colombia. The emeralds found there are from deep green color and highest purity - factors that make up the value of green gemstones and also affect the price of the Colombian emeralds knock down.

The streak color of emerald - that is, the color that appears when a mineral is painted over an unglazed porcelain tablet, the streakboard - is always white.


Emerald - Our recommendations *



Color and purity correction of emerald

In gemology, it is customary to correct the color of minerals and gemstones - corrections in the form of intensification, enhancement, or change to an entirely different color. In addition to firing, methods of color correction are also radiation, coating or oiling.

Intensifying the color of emerald is difficult. In contrast to many other minerals, which react with a stronger hue or a different color when exposed to heat, the green gemstone did not resort to the so-called burning become.
The reason: the numerous Fissures and cavities in the emerald. When heated, the Risk of the stone breaking completely.

Instead, emeralds focus on the Focused on optimizing purity. Synthetic resin such as epoxy resin, natural resin, or oil are embedded in the cavities of the stone. In this context, it has above all Cedarwood Oil proven, whose Refractive index approximately the same as that of emerald is. The result: by filling up the gemstone appears clearer and purer, at the same time the color appears more homogeneous and more intense. Colored oil is sometimes used.


Emerald and emeraldite

Emerald and emeraldite are two different minerals, despite their similar names and comparable colors.

propertyemeraldEmeraldite
Chemical composition Al2Be3(Si6O18)Approx2(Mg, Fe)5Si8O22(OH)2
Mineral grade Silicate mineral / beryl varietySilicate mineral / actinolite variety
colourgreengreen
Line color WhiteWhite
shine glass-likeglass-like
transparency transparent to translucenttransparent to translucent
fracture uneven, mussel-likeshell-like, brittle
Cleavage imperfectperfectly
Mohs hardness7.5 to 86
density 2.6 to 2.8 g / cm33.3 g / cm3


Trapiche emerald

Trapiche emeralds are a variety of emeralds, their main characteristic black drawings radiating out from the center of the mineral are - embedded in the emerald green matrix.

Because of the resemblance to wagon wheels, those emeralds were given the name, which comes from Spanish Trapiche for wagon wheel.

Investigations have shown that the black deposits are the mineral lutite or carbon compounds.
The formation of trapiche emeralds has not yet been definitively researched, although it is likely that spatial restrictions in crystal growth are the cause. Trapiche emeralds are mainly found in Colombia and are bound to the rock slate.


Origin and distribution of emerald

Emeralds arise as a result of rock metamorphosis or crystallize from rising magma.
The prerequisite for the formation of metamorphic, secondary emeralds are, in addition to temperatures around 500 ° C and pressure ratios around 7,000 bar, the existence of beryllium-containing pegmatites and chromium. The emerald crystals grow either in rock corridors or on rock walls.

The occurrences of emerald are accompanied, for example, by albite, apatite, aragonite, barite, calcite, dolomite, fluorite and pyrite.

Notable emerald deposits can be found in Norway; France; Hohe Tauern / Austria; Switzerland; Italy; Czech Republic; Bulgaria; Nigeria; Namibia; Mozambique; Zimbabwe; Tanzania; South Africa; Madagascar; Russia; Kazakhstan; Pakistan; Afghanistan; India; China; Australia; Colombia; Brazil; Canada and the USA.


Uses and meaning of emerald

The green gemstone emerald is mainly processed into jewelry (necklaces, rings, earrings, bracelets or pendants), but it is also popular as a mineral in collections. Extensive emerald collections can be found, for example, in the British Museum of Natural History in London, the American Museum of Natural History in New York, in the Russian State Treasury or in the Vienna Treasury. The world's largest collection of emeralds is stored in the central bank of Bogota / Colombia.


Emerald healing stone

In addition, emerald is traded as a chakra stone / healing stone, which Hildegard von Bingen already worked with, without the healing properties of emeralds having been proven in clinical studies.
Furthermore, emerald is considered a lucky stone for those born in May (so-called month stone or birth stone) and as a side stone for the zodiac sign Cancer.


Emerald jewelry and emerald cut

As a stone for jewelry, emeralds are kept in particular in facet cut.

In the past, a cut was developed specifically for the green gemstone, which is known as Emerald cut (English: emerald cut) became known.
The hallmark of the emerald cut is the basic rectangular shape and the stepped facets. Originally, the emerald cut was only used for emeralds, but is now also applied to other clear minerals.

The processing or grinding of emeralds can be difficult. The mineral is brittle and splintering due to possible inclusions and cracks. In order to give emeralds more hardness or durability, the stones are subsequently "sealed" with a fine layer of plastic or resin for protection.

In addition to the emerald cut, the following cuts are also used: oval cut, round cut, square cut, pear cut, navette / marquise cut and antique cut.
Particularly cloudy emeralds, on the other hand, are given smooth cuts, which focus on increasing the luster and the "pattern" in the stone. One of the most popular smooth cuts is the cabochon cut, in which the stone is simply shaped and polished. Facets, on the other hand, are missing.


Raw stone jewelry with emerald

While classic emerald jewelry relies on faceted emeralds, raw stone jewelry builds on the beauty of unprocessed stones.

The trend is not new; Rough stones have been drilled for centuries so that the stones can be worn as a chain. What is new, however, is that rings and earrings are now also provided with rough stones. Most of the time, the untreated, natural stones are held in place with a bezel or prong setting.

A major advantage is the price of these stones. Compared to a stone of the same weight, uncut emeralds are much cheaper to get in jewelry. The proportion of the perfect cut or the processing in the price of a gemstone is up to 40%.


Imitations, forgeries and mix-ups

As with almost every mineral, there are also stones in emeralds that can be confused with the green gemstone due to their color.
In particular, the green of demantoid, diopside, dioptase, grossular, hiddenite, peridot, green tourmaline and uvarowite comes very close to the color of emeralds.

Furthermore, quartz, spinel or glass, zirconia and emerald syntheses are sometimes in circulation in the trade. The first successful synthesis took place in France in 1848.

The trade names of numerous minerals and emerald syntheses that have the term emerald in their names are also confusing, even if it is a different mineral and gives the appearance of a variety. The motivation behind trade names is different. In most cases, the addition of emerald to the name aims to increase the value of apparently inferior minerals; for example:

  • Biron emerald: Emerald synthesis
  • Chatham emerald: Emerald synthesis
  • Emeralda: Emerald synthesis
  • Gilson emerald: Emerald synthesis
  • Igmerald: Emerald synthesis
  • African emerald: Fluorite
  • Brazilian emerald: Tourmaline
  • Copper emerald: Dioptas
  • Night Emerald: Peridot

The largest emerald in the world

Emeralds sometimes form very large and heavy crystals. The largest emerald crystal bears the name Bahia emerald, comes from the beryl mines in Bahia / Brazil, was discovered in 2005 and weighs 341 kg.
In January 2018, the discovery of a 1.6 kg emerald crystal caused a sensation in Russia. The green crystal was found in the Malyshev emerald and beryllium plant in Sverdlovsk, is 17 cm with a diameter of 7 cm.

Two emerald crystals that were discovered in Zambia in 2018 are also a sensation: the 6,225 carats (= 1.245 kg)heavy Insofu- Emerald alias The Elephant Stone as well as the Inkalamu- Emerald or lion emerald with a weight of 5,655 carats (= 1.131 kg).


Postage stamp emerald 2012

In January 2012, Deutsche Post published a series of stamps entitled "Gemstones". In addition to a cut emerald (see picture), a ruby ​​and a sapphire are also depicted on the welfare stamps.



Detection and determination of emeralds

Emerald is not soluble in acids, has no fluorescence, glows intensely red in the Chelsea filter. Characteristic is the emerald's own dichroism, which appears in green-blue and green-yellow.


Also interesting:
⇒ The emeralds from Habach Valley in Austria
⇒ Green diamonds
⇒ Pink emerald, or emeralds that aren't



Swell:
⇒ Bauer, J .; Tvrz, F. (1993): The Cosmos Mineral Guide. Minerals rocks precious stones. An identification book with 576 color photos. Gondrom Verlag GmbH Bindlach
⇒ Medenbach, O .; Sussieck-Fornefeld, C .; Steinbach, G. (1996): Steinbach's natural guide minerals. 223 species descriptions, 362 color photos, 250 drawings and 30 pages of identification tables. Mosaik Verlag Munich
⇒ Pellant, C. (1994): Stones and Minerals. Ravensburger nature guide. Ravensburger Buchverlag Otto Maier GmbH
⇒ Schumann, W. (1991): Minerals rocks - characteristics, occurrence and use. FSVO nature guide. BLV Verlagsgesellschaft mbH Munich
⇒ Schumann, W. (1992): Precious and precious stones: all precious and precious stones in the world; 1500 unique pieces. BLV determination book, BLV Verlagsgesellschaft mbH Munich
- News entry www.steine-und-minerale.de (January 2, 2012): Welfare brands precious stones
- www.de.sputniknews.com - An emerald weighing a kilo discovered in the Urals
- www.mindat.org - emerald
- https://gemfields.com - GEMFIELDS introduces "Inkalamu", the 5,655 carat Lion Emerald

Reading tip: www.lapisphilatelie.de - a collection of stamps with a focus on minerals and geology

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