Gemstone

Precious stones, sometimes also referred to as gemstones, minerals, rocks or glass melts, which are generally perceived as beautiful and as jewelry are used, but also substances of organic origin, such as amber, Pechkohle or relatively small and shapely fossils. According to the definition of the International Trade Organization CIBJO also include pearls, mother of pearl and coral to the jewelry stones.

The doctrine of precious stones and semi-precious stones is known as gemology.

• 2.2.1 classification

• 3.1 oils / fats
• 3.2 waxing / waxing
• 3.3 stabilize
• 3.4 reconstructions
• 3.5 dyeing
• 3.6 Burn
• 3.7 irradiating
• 3.8 synthesis
• 3.9 imitations 3.9.1 doublet / triplet
• 3.9.2 identification

General History

Probably since the Paleolithic stones are also used as jewelry use. In ancient times, gems were processed in addition to gold, silver and other materials for jewelry. Gemstones were used early ruby, emerald, sapphire, and beryl. As a gemstone but also found the use of amber.

Since gemstones usually represented also a considerable value, they were not infrequently fake. The color of some minerals, such as agate, was altered by burning or staining. These and some other traditional "improvements" must not be declared. If, however, by irradiation with electromagnetic waves to color changes, this must always be specified.

In ancient and medieval jewels were ground only more or less round. The facet cut arose only in the early modern period. Also, the diamond has become only in modern times for jewelry stone, while it was used in ancient times due to its hardness of craftsmen, such as the carving of cameos.

Minerals

Minerals in the appropriate quality often as precious and gemstone use. As a function of the mineral type (e.g., diamond, corundum, malachite ), different criteria for determining the quality can be used. The site can make a difference in fine details of individual expression, which in turn reveal a specialist in the origin of the stone.

Often, it is the transparency, purity, rarity and color over the use and value. Some minerals have inclusions that reduce the value of the stone, but can also increase. In one of the most valuable gemstones, the diamond, pulling four properties (4 C ) bring to the cut ( Cut), the weight in carats ( Carat ), the color ( color) and the purity ( Clarity ), of which for a long time can only affect the first man directly. In the meantime, however, can also the diamonds around inclusions that affect the purity, artificially reduced.

Gemstones are heat-treated, or radioactive partly in order to improve their optical properties or change. The color of some amethysts proposes, for example after a heat treatment from purple to yellow. Subsequently, the treated mineral is marketed as " citrine " in the trade. In Germany, these artificially treated minerals need, such as color changes should be labeled accordingly.

Minerals in gem quality are also produced synthetically, such as quartz and its variety amethyst or corundum. The quality of synthetic diamonds could be greatly improved in recent years, so these are also used as a gemstone.

Gems

Gemstones are gemstones that meet the following three criteria:

• Rarity
• Mohs hardness > 7
• Transparency

Known gem types include ruby, sapphire, emerald and topaz. A diamond is a special crystalline manifestation of elemental carbon. According to the above definition, he also is one of the gems while as a gemstone had no particular value in the Middle Ages and usually only the colored stones were called gems.

Most gemstones are now ground to forms which increase light reflection and increase the quality of the polish to shine, but also to the mineral to give a form suitable for further processing in the form of jewelry. Only in ground in brilliant cut diamond is called diamonds, other precious stone types brilliant-cut must be supplemented by the gem name.

Classification

In addition to the above already mentioned classification features, such as light transmission, clarity and color, there are, among others, the following criteria, which are based on the criteria of Mineral determination:

Among the criteria used initially counts the chemical composition, diamonds for example consist of carbon, rubies from chrome -colored aluminum oxide ( Al2O3). Furthermore gemstones are also distinguished by their crystal system, the nature of the crystal lattice, which may be, for example, cubic, trigonal or monoclinic. The so-called habit, the form in which the gem is to be found in nature, is another classification criterion.

Gem species are often further divided into different varieties, depending mainly on the color. So red corundum is approximately treated as a ruby, a special red-orange as Padparadscha. The remaining colors are referred to as sapphire, while the blue sapphire is the most valuable. Even diamonds can be found in different shades, which are then known as "fancy diamond". The varieties of beryl find as Emerald (green), aquamarine (blue), red beryl (deprecated also Bixbite, red), Goshenite (colorless), beryl ( lemon yellow to golden yellow ) and Heliodor (light green ) or morganite (also Rosaberyll ). Heliodor is however partially rejected as independent beryl variety and counted among the Goldberyllen.

Physical differences manifest themselves in the refractive index, dispersion, specific gravity, hardness, cleavage, brittleness and gloss. Precious stones like tourmalines can pleochroism in different directions show different colors or be birefringent. Another characteristic is its absorption spectrum.

For the value of a gemstone finally his size plays a significant role.

" Semi-Precious Stones "

As semi-precious stones were referred earlier minerals, which are distinguished by their beauty, in contrast to the precious stones but much more frequently found in nature. They are usually less severe and less valuable than precious stones. Today we hear only of precious stones or semi-precious stones. The term semi-precious stones is obsolete and should no longer be applied in mineralogy and gemology. He suggests a certain inferiority, which is actually not available.

Classification

The usability and the value of a gemstone / gemstone based on criteria that are highly dependent on the mineral species. So there are no other criteria than the glitz and potentially the shape of ores such as hematite and pyrite. In grenades, quartz and other minerals play similar gems light transmission, clarity and color play a role

Manipulation and imitation

Many minerals or rocks, which are used as a gemstone be manipulated in various ways to improve their properties ( color, luster, durability ) and thus to make more desirable or imitate other rare and precious gemstones.

Oils / fats

One of the oldest methods, supplement stones, the oils, in order to cover over cracks. The stone looks transparent and the colors more vivid and intense (compare between wet and dry river pebbles ). The oils used range from animal oils ( spermaceti, tallow ) on vegetable fats ( vegetable oil, olive oil or sunflower oil ) to synthetic oils and even baby oil ( petroleum jelly).

Oiled stones "sweat" the oil when heat is easily made ​​, also it dries with the time. Both lead to staining and loss of gloss. Oiled rough stones and minerals may be completely unusable under certain circumstances by the formation of a non- washable, ugly coating. Only when using colored oils of the additional duty is colored. However, it is considered by collectors to be incorrect, if they are offered such items without any labeling, since the optical impression of the pieces ( wertbestimmend! ) is significantly altered.

Waxing / waxing

Instead of oil you can also use wax or paraffin mask cracks and enhance gloss and color. The waxing is a bit more durable and is primarily used for opaque gemstones and drum stones used. However, the wax is removed over time through use or excessive heat exposure. The paraffin treatment, it is colorless, need not be specified in the trade. This method is not considered by collectors.

Stabilize

Soft, porous or coarse gemstones are treated with a coating of resin or resin to protect them (sweat, soap) from damage due to scratches and chemicals. However, this color can also be changed by use of colored resins. Stabilized Gemstones must bear the additional treated.

Reconstructions

Reconstructions are mainly in opaque stones widely used, but also in amber, this method is popular. This powdered material or small fragments are either fused together (Bernstein ), sintered ( hematite) or glued with a suitable binder ( malachite, turquoise ). Reconstructions of amber may be referred to as "real amber ", hematite, however, is renamed to hematin. All other gemstones which have no separate business name must, as a " reconstructed " are referred to.

Gemstones with unwanted or pale color are recolored with various, mostly superficial, ways to help them upgrade. All colored gemstones must also be referred to as such.

Firing

Blowing means that the raw semi-precious stones are heated up to several hundred degrees Celsius in order to change the color and transparency. Colouring metallic inclusions are oxidized in the process, crystallization error and thus resolved opacities. Depending on the temperature and burning time different gemstones can get different shades. In the conversion of, for example Amethyst Citrine in a light yellow, between 550 ° C and 560 ° C. However, this takes at a temperature of about 470 ° C on a dark yellow to reddish-brown color. Smoky quartz can be partly already at 300 to 400 ° C to convert. Burning the stones permanently changed, but is difficult to detect.

Particularly lucrative is the burning of certain, cheaper, milky white sapphires, so-called Geuda to cornflower blue color. An increase in value from 10 - to 100-fold is possible. Even already faceted stones can then be burned if they are einschlussarm.

Burnt bricks must not be specified as such. In order to avoid misleading, however, it is not permissible to use for artificially treated stones fancy names.

Irradiate

Also, the irradiation with X-rays or Radioactive rays ( gamma, neutron or rare alpha rays ) is used to color change, which can be very strong, but is in contrast to the burning does not always last. In addition, in the stone occur during irradiation with neutrons radionuclides that can become radioactive under the circumstances gemstone. You must, therefore, until resolution of the radiation in quarantine, which can partially take several years. All these altered gemstones must wear treated or irradiated the addition.

Synthesis

Some minerals can be prepared from the corresponding basic elements of artificial ( synthetic), for example by the Verneuil process. For the production of certain minerals heat and pressure, however, are also necessary. The diamond is the best example, but also many other minerals are now synthesized in very good quality and have only minor differences to their natural counterparts on. Syntheses are especially widespread in addition to the diamonds and rubies and sapphires, emeralds, opals and quartz oscillators. All syntheses must be marked as such.

Today in toys houses special chemistry sets offered, but only crystals of semi-precious stones like appearance produce (usually by recrystallization of potassium alum or similar, harmless salts and the presence of color additives from saturated aqueous solution).

Syntheses are often used for jewelry because they are contrary to your naturally developed models usually cheaper to produce. , May be prepared cheap trinkets, the syntheses of which are artificially produced almost indistinguishable from genuine semi-precious stones.

Imitations

As seen many minerals very similar, especially in color, are rare and therefore expensive often imitated by more frequent and thus cheaper minerals. A common imitation is synthetic spinel, which can be produced in many colors. It is even simpler, imitations using glass or ceramic to produce. In order to distinguish real gems from fakes, their physical properties are analyzed.

Doublet / triplet

A special case of imitation is the doublet or triplet, consisting of composite layers of genuine gemstone and glass, syntheses, quartz or other solid bodies. With this method, you can make many little stones from the base material. Although it is used, for example, real opal, but it is a massive manipulation of the stone. Triplets and doublets are declared.

When duplicates are a thin layer of genuine gemstone, which is glued to a backing made ​​of obsidian, various iron stones, Potch ( opaque opal without play of color ) or even plastic. This preserves the delicate stones among other things, body and thus welding contact. For triplets, there are correspondingly two covering layers, the base protects against physical contact, the topsheet from scratches and dehydration and is therefore particularly often used for opals. In order to recognize doublets or triplets, the stone usually has to be taken out of the socket.

Identification

To find out counterfeiting, tampering, or imitation, the density or translucent minerals of the refractive index of the to be examined Gemstones can be used. For the determination of the refractive index to use a refractometer. Another method, spectroscopic investigations with which the spectral distribution of the characteristic absorption lines can be analyzed in the absorption spectrum.

A simple method for roughly determining the refractive index is the so-called immersion method, in which the to be tested are immersed in liquids gemstones of known refractive index. These make the contours of the immersed object in accordance index of refraction disappear.

With the help of fluorescent certain gemstones can also be identified. For excitation by light, especially the two ultraviolet wavelength ranges between 200 and 280 nanometers and 315 nanometers and 400 are used. The stones then glow in distinctive colors in visible light.

Esoteric

Many gemstones found in the esoteric as a healing stone or use in amulets to protect against bad influences.