The Gemstone Amethyst

Amethyst is the purple variety of Quartz with chemical composition indicated by the formula SiO2. This Amethyst belongs to the Tectosilicates mineral class. This Amethyst is a very popular gemstone that is commonly less expensive due to its widespread availability. It can be used as a mineral specimen and it can be also cut for gemstone purposes. Crystals are trigonal and sometimes in hexagonal prisms. They can be found in pyramidal form having dipyramidal ends. Between crossed nicols of polarizing light microscopes, it usually appears striated on prism faces. There can be gas or liquid inclusions found appearing in dark border when evaluated between crossed nicols of petrographic polarizing microscopes. Amethyst is the purple variety of quartz, Rose quartz is the pink variety, the yellow variety is called Citrine, the gray-black variety is termed Smokey quartz, and Jasper is the red variety of quartz. All varieties do exhibit splendid and fascinating appearance under polarizing light microscopes. This gem is also considered as a birthstone for the month of February. Minerals cut for gemstone purposes are beautifully brilliant when viewed under gemological microscopes.

The color of the Amethyst mineral was ones attributed to the presence of manganese as noted in the 20th century. But this mineral is capable of great alteration and can be actually discharged by heat. The color of the Amethyst mineral was then believed to be from an organic source by some authorities. Sulfur was then detected present in the mineral by ferric thiocyanate. Alternate lamellae of right-handed and left-handed quartz in irregular superposition compose the Amethyst mineral. This structure is maybe due to some mechanical stresses. It has been known that Amethyst may show thumb markings or can possibly break with rippled fracture as a consequence of its composite formation. A fractured surface with some patterns like that of the engine turning maybe produced by possible intersections of two sets of curved ripples. Amethyst name is applied to all quartz that exhibits this type of structure, regardless of the purple color displayed under polarized microscopes, by some mineralogists following Sir David Brewster.

Amethyst derived its name from a Greek word “amethustos”, which means not drunken. Some consider that this is relative to one of the metaphysical powers of Amethyst, which is its ability to ward off alcohol effects. Early Greeks also believed that drinking wine from an Amethyst cup would prevent intoxication. To the Greeks, it is an allusion to the wine-like color of the gemstones that they have encountered. Ancient cultures use amethyst amulets as antidotes against poison, as protection against harm in battle, and to dispel sleep. Amethyst has been used to adorn the rich and powerful rulers and monarch in history because its purple color traditionally symbolizes the color of royalty. At present times, Amethyst is considered as an affordable lovely gemstone most especially when it is examined under gemological microscope, which is already in wide availability that we can possibly possess. Several varieties, cut or uncut are greatly admired.

Amethyst crystals usually occur in long prismatic crystals with fascinating appearance in transmitted light of polarizing light microscope. Crystals commonly occur in horizontally striated hexagonal prisms with combinations of positive and negative rhombohedrons forming six-sided pyramid terminations at either end, which are commonly visible under petrographic polarizing microscope. They may also appear in massive formations. They can also exhibit crystalline crusts druzes formation showing pointed terminations. Amethyst crystals commonly appear in purple violet to deep purple shades in transmitted light of polarized light microscopes. Crystals usually vary in transparent and sometimes in translucent appearance. Using Mohs scale, the hardness of the Amethyst mineral is usually 7. Because of this hardness measure of Amethyst mineral, it is considered a treasure in its use in jewelry. However, it has been known that Amethyst is not as hard as diamond. When mineral is rubbed on a white plate, it usually shows white streak. Specific gravity of Amethyst is approximately ranging from 2.64g/cm³ to 2.69g/cm³. Dauphine and Brazil twins are found between crossed nicols of polarizing geological microscope. It shows distinct pleochroism under polarizing microscopes. Amethyst usually show vitreous luster in reflected light of petrographic polarizing microscope. Cleavage is absent in all directions, and it shows conchoidal fracture in transmitted light of polarized light microscopes.

Amethyst as a mineral specimen is very much popular for its wine-like purple color with nice and handsome purple crystals in sparkling clusters with majestic appearance in petrographic polarizing microscope. This crystal when viewed under a polarized light microscope certainly exhibits an exquisite beauty and splendor for most mineral collectors. The color of Amethyst is commonly considered as unparalleled splendidly displayed in polarized light of geological microscopes. It is usually compared to most expensive purple colored gemstones. The gemstone has to have wide range of purple shades for it to be considered as Amethyst. As a gemstone, it has brilliant and fascinating appearance when viewed with the aid of a gemological microscope. Amethyst cut gemstones are usually presented from high-, medium-, to low-grade variety by labeling them as Siberian, Uruguayan, or Bahain respectively. Brilliant round cuts are the usual gem cut of Amethyst in order to maximize the color. This is because Amethyst commonly has patchy color distribution. It can be also possibly cut in other manner if colors are better distributed.

Amethyst mineral usually occur in siliceous volcanics. They commonly occur as druzes covering the insides of the agate lined vugs. They may also form as geodes. Amethyst crystals are usually formed in quartz veins. Amethysts do have different varieties in different types of locality. They cannot be seen the same everywhere in the world. A unique variety of Amethyst can be produced from a different mining area, region, or type of locality. A particular Amethyst can be used to distinguish its source or mining area through its color, crystal shapes, associations, character formations, and inclusions found when it is evaluated between crossed nicols of petrographic polarizing microscope.

There are several types of localities and attributes characterizing the type of Amethyst mineral found in the said area. In Minas Gerais and Rio Grande do Sul, Bahaia, Brazil, an Amethyst mineral type found is having crystals in druzy crust formation that are usually found lining the inner section of some large vugs or volcanic rock pockets. Some of these vugs may appear quite large. They can be also found formed in different areas. Some vugs are formed from lava flow engulfed trees for millions of years that usually withered away. Others turn out as just gas bubbles in the lava. This type of Amethyst minerals usually exhibits light to medium crystal color where the only colored parts are the crystal tops exhibiting splendid appearance under petrographic polarizing microscopes. If they happen to form in clusters, they usually appear in gray, blue and white agate with green exterior on the vugs usually visible in transmitted light of polarized light microscopes. This Amethyst type is commonly associated with calcite mineral. It commonly shows cacoxenite inclusions when evaluated between crossed nicols of polarizing geological microscope. In another locality of Brazil, in Maraba, Amethyst crystals are commonly found in large masses. They are usually having unattractive surfaces exhibiting pale to medium color of crystals in transmitted light of polarizing microscopes for geologists. Its crystals are often carved and cut into slices. In Vera Cruz, Mexico, Amethyst crystals are commonly pale and clear in appearance in transmitted light of polarized microscope. They usually occur in prismatic crystals, which are doubly terminated commonly visible under petrographic polarizing microscope. Light colored rocks usually host these Amethyst crystals, which can be visible with the aid of an ore polarizing light microscope. These crystal types of Amethyst are usually phantomed. Some others may be sceptered. Phantomed crystals usually have clear quartz interior and the exterior is usually the purple Amethyst. A deep, dark purple variety of Amethyst can be found in Guerrero, Mexico. It usually forms in prismatic crystals that are radiating outward from a common attachment point. These Amethyst crystals are usually phantomed having Amethyst interior and clear or white quartz exterior. Phantoms are commonly opposite to that of the Vera Cruz. These Amethyst crystal types are considered as the most valuable Amethysts in the whole wide world. In Africa, amethyst crystals are usually in large masses and commonly not attractive. These Amethyst crystal types usually have excellent interior color and clarity. Its crystal carvings, polished slices, and gemstones are usually admired and prized. Amethyst crystals with hematite inclusions in distinct red color, which is visible under polarizing microscopes, are uniquely found in Thunder Bay, Canada. These inclusions that are usually visible in transmitted light of polarized light microscope are commonly found just below the crystal surface of Amethyst mineral. They commonly form in druzy crust clusters usually found lining the fissures formed in ancient metamorphic rocks. In Italy, crystals of amethyst mineral are usually found similar to that of the ones found in Vera Cruz but with slight differences. This Italian Amethyst is not as well defined as that of the Vera Cruz. They are usually found growing in parallel clusters exhibiting good colors that are commonly evenly distributed. In Uruguay, Amethyst crystals are commonly found in dark to medium colors in transmitted light of polarizing light microscopes. They are commonly found in druzy crust formation usually lining the inside of the volcanic vugs, which have brown or gray exterior. These crystals are usually found colored throughout with multicolored agate formation and often times contain shades of orange, red, and yellow in polarized light of polarizing geological microscope. Amethyst crystals that are commonly coating stalactites may be found forming inside volcanic vugs. Other unusual formations may also occur in these vugs. Amethyst crystals found in Germany are commonly associated with colorful agates forming light-colored druzy crusts. A very clear and dark variety of Amethyst crystal is found in Ural Mountains of Russia. These crystals are commonly cur for fine and expensive Amethyst gems. With this crystal variety of Amethyst, natural uncut clusters are rarely found on the market. In different parts of USA, there are also different varieties of Amethyst crystals. Druzy clusters of Amethyst exhibiting bluish-violet tints in transmitted light of petrographic polarizing microscope are found in North Carolina. Those varieties with druzy clusters, which are filled fractures in metamorphic rocks, are commonly found in Pennsylvania. These varieties are commonly exhibiting patchy brownish purple colors in transmitted light of polarizing light microscope. Dark druzy clusters of Amethyst crystals are found in Maine but are not widely distributed. In Colorado, druzy crusts in cluster crystal formations are found inside the fissures of sandstone. They are commonly found on top of the crust of green fluorite exhibiting splendid view under polarizing microscopes. The crystals of this Amethyst variety are usually small and dark colored when evaluated under polarized microscopes.