Gem
A gem, also called a precious stone, is a rock, mineral, glass or organic product of natural origin, which, when cut or polished, can be used in the making jewelry or artistic objects. They are precious mineral stones such as ruby, diamond, emerald, sapphire; semiprecious like spinel, alexandrite, tanzanite or garnet; natural glass such as obsidian; rocks such as malachite, lapis lazuli or onyx, fossil products of organic origin such as jet or amber and biogenic products such as pearls (produced by an oyster) or coral (formed by the calcareous secretion of small marine polyps).
For the World Jewelry Confederation, a gem is, strictly speaking, a precious stone —always of natural origin—, of very high quality or perfection.
General information
Some stones are manufactured to imitate other gems. However, synthetic gems are not necessarily an imitation. For example, the diamond, ruby, sapphire and emerald created in laboratories have the same physical and chemical characteristics as the original item. Small man-made diamonds have been mass-manufactured for several years, although only recently have quality large diamonds been created, especially those of varied and striking colors.
A gem is valued primarily for its beauty and perfection. In fact, the appearance is most important. Beauty must also be lasting; if a gem is damaged in any way, it instantly loses its value. The characteristics that make a stone beautiful are its color, an unusual optical phenomenon, a fossil-like inlay, its rarity, and sometimes the peculiar shape of the crystal.
Traditionally, gems were divided into two large groups: precious stones and semi-precious stones, without further ado. Until now, they are considered four precious gems:
- Diamond
- Emerald
- Ruby
- Zafiro
And semi-precious, such as:
- Agate
- Aguamarina and other varieties of berylo
- Alexandrita
- Amethyst
- Amber
- Ametrino
- Apatite
- Azurita
- Calcedonia and its varieties
- Cornalina
- Crisocola
- Quartz and its varieties
- Spit it out.
- Jade
- Jaspe
- Lapislázuli
- Malachi
- Obsidian
- Tiger eye
- Oil
- Peridote (a variety of the sheep)
- Perla
- Pirita
- Topaz
- Turmalina
- Turquoise
- Zircon
However, today, gems are described and differentiated by specialists by certain technical specifications. Among them, what they are made of, their chemical composition and even their color. Diamonds, for example, are made of carbon (C). In the case of cut diamonds, for example, their value will depend on the so-called "four Cs": carat (carat), cut (cut), colour, (color) and clarity (transparency).
On the other hand, many gems and crystals are classified by their shape, into different groups, species and varieties. For example, the emerald is of the green variety; aquamarine is blue, bixbite is red and morganite is pink. All these varieties are of the beryl species.
Gem properties
Beauty
- Color
- Colorless (leucozafiro, diamond)
- Gems of color: red (rubi, rhoonite), dark blue (sapphire, tanzanite), green grass (smerald), light blue (aguamarine), yellow (topacio), pink (morganite)
- Idiochromatic: with its own color
- Alochromatic: by impurities
- Seudochromatic effects: optical effects
- Lustre: depends on the nature of the gem and the type of link.
- Adamantino: diamond
- Resinous Admantine: Circle
- Nacarado: pearls
- Sedose: materials with targeted inclusions (rounded quartz, cat eyes)
- Crasus: turquoise
- Resinous: Amber
- Céreo: jade
- Graso: azabache
- Transparency
- Transparents
- Semi-transparent/translucent
- Opacos
- Optical effects:
- Opalescence: milkiness in material
- Adventurescence: reflection of light in inclusions, metallic shine.
- Colors game: diffraction of light (noble eyes)
- Adularescence: blue reflex
- Labradorsce: reflection of light in an opaque stone, metallic shine (laughter)
- Asterism: inclusions in the form of a star-shaped needle (small rabbis and sapphires) or with four tips (Indian stars)
- Cat eye: inclusions in an address
- Fire: scattering of light (need facets) diamond, zircon, fabulous, garnet
- Iridiscence: interference of light in colors by a fissure in stone (arzo iris)
Durability
- Hardness: scratch resistance (see hardness scales)
- Vectorial: property that changes according to direction
- Exfoliation: Minerals can be separated into flat sheets (you can never carve a facet according to the exfoliation plane)
- Complete: in romboedros (mica)
- Midsize:
- Null: (square, garnets)
- Partition or false exfoliation: maclas (corindones, rubies and sapphires)
- According to the number of exfoliation planes: 2 (smerald), 4 (diamante), 6 (calcite).
- Fracture:
- Fragile: does not bear a brusque blow (quartz,topace)
- Tenaz: Do not break (diamante,jade)
- Resistance: physical and chemical agents
- Pearls: acids and alcohol/ambar: alcohol
- Heat: they do not support it (amber, azabache, opal, pearl); they change color (amateur)
Rarity
- Few: diamonds have long been mostly owned by De Beers, although since 2004 they have less than 50% of the market.[chuckles]required]
- Gem classes: properties of a material, depend on chemical composition and structure.
- Natural, fine or true Gems: with allowed treatments (heating of the zircons and marine water, friture of the emeralds)
- Synthetic geomes: laboratory (distinguished by inclusions)
- Artificial Gems: its composition and structure varies from natural (circonite, fabulous)
- Composite Gems: they are made by uniting pieces of other gems.
- Reconstituted Gems: by heat and pressure (amber, carey)
- Gems of imitation
- Glasses
- Pearls
- Natural: they generate mollusks (calcium and conquiolina)
- Oriental: painted oysters and mother-pearl
- Cultivated: raised in fish farms
- Imitation: glass with varnish (not officially considered gems)
Fakes
- Quartz crystal: It is colourless and is forged using glass. The most forged form are the spheres, which have microscopic bubbles of less than one millimeter and also contain an interior with very subtle scratches. The quartz crystal is harder than the glass, so it scratches it. The problem of the test is that sometimes the quartz breaks if the tip is weak. The quartz crystal, when it is of medium quality, presents impurities and as a kind of white "cloths" inside it. There are also fully transparent quality quartzes that look like glass.
- Lapislázuli: It is a blue stone originating in Afghanistan and Chile.
- The lapislázuli Afghan It is the best quality, its counterfeitings use pirita inlays to make it pass by mineral of more value. Other forgeries use the mixture of ground stone with paints and usually present lapislázulis of very opaque or very bright colors with piritas.
- The Chilean lapislázuli is falsified by staining the same stone or similar with blue dye to make it more attractive to give it value, others usually present large pieces of lead, white and blue color.
- Cuarzo citrino: It is extremely difficult to get authentic minerals on the market. The yellow quartz is scarce in nature, so it is counterfeited with amethyst, abundant mineral, that although it is purple when it heats it at temperatures around 300 °C, it changes color as it cools, appearing to be cytrino. The way to detect the false stone is that it has a more golden chromatic tone and with touches of brown with white spaced, characteristic of the amethyst that crystallizes in the form of geodes.
- Turquoise: It is almost impossible to determine the forgery, using a mixture of white stone with dye. The true turquoise is also muted and a mixture is made to shape the stone. The true turquoise always seals with a film that protects it from the sun, because it is dense in a natural state.
- Amber: In addition to imitations with artificial materials, such as baquelita or pérspex (polymethylmethacrylate), or even glass, imitations with natural materials are made of copal resin, of the kauri pine (Agathis australis), of New Zealand, of the Hymenaea courbariof South America, or of the lady's resin (Belanocarpus heimii) from Malaysia, Indonesia and the Philippines.
Origin and growth
- Magmatics: magma crystallization.[chuckles]required]
- Sedimentaries: crystallization during the diagenesis.
- Metamorphic: crystallization and recristalization by pressure and/or temperature of pre-existing rocks.
- Hydrothermals: from fluids at high temperatures.