Geological Properties Of Amethyst
Geological Properties Of Amethyst, Amethyst is a violet variety of quartz often used in jewellery. The name comes from the ancient Greek ἀ a- (“not”) and μέθυστοςméthystos (“intoxicated”), a reference to the belief that the stone protected its owner from drunkenness. The ancient Greeks wore amethyst and made drinking vessels decorated with it in the belief that it would prevent intoxication. It is one of several forms of quartz. Amethyst is a semiprecious stone and is the traditional birthstone for February.
Amethyst color
The colour in amethyst from most localities is unevenly distributed in the individual crystals. In amethyst geodes it is often most intense in the growth zones under the rhombohedral faces (at the tips). Occasionally the colour is deeper under either the r or z rhombohedral faces, giving the crystal a pinwheel appearance when viewed from the top. In prismatic crystals the colour may appear in phantom-like thin layers, while in sceptres and skeleton quartz the colour is often concentrated along the edges, and accompanied by smoky zones. Despite the intense colour, the content of iron occupying Si positions in amethyst is rather low, in the 10-100 ppm range.
When heated to more than about 300-400°C, amethyst loses its violet color and often turns yellow, orange or brown, and then resembles the quartz variety citrine, but depending on the locality and the temperature during the heat treatment it may also turn colorless or rarely green.
Irradiation with UV light will also destroy the color centers, and accordingly prolonged exposure to sunlight will slowly fade amethyst. The photo to the right shows the effects of heat (bottom left and right) and UV irradiation (top right) on the color of a specimen from Uruguay.
Geological Properties Of Amethyst
Amethyst is pleochroic when the polarization of the light is changed from parallel to the c-axis to perpendicular to the c-axis, amethyst changes its color from blue-violet to purple. The strength of the effect varies to a considerable degree, and changes in the hue depending on the direction of the transmitted light may be observable with the naked eye, in particular in crystals with a zonar development of color, which may even show sky-blue tones.
Amethyst Crystals
Amethyst crystals do not get very large, crystals longer than 30 cm are very rare. It is found in various forms and shapes, the most common growth forms are:
Druzy crystal aggregates that outline cavities; the crystals are usually short-prismatic and often lack prism faces. Most common in volcanic rocks, but also in hydrothermal veins, and even in cavities in sedimentary rocks;
Scepters (late syntaxial overgrowth) on other color varieties of quartz, in particular in high- to medium-temperature environments like alpine-type fissures and pegmatites
Split-growth crystals (“artichoke quartz”) in hydrothermal veins in ore deposits, but also in volcanic rocks.
As individual well-formed crystals in small cavities and fissures, in particular in volcanic rocks.
As hydrothermal vein filling, often with several growth phases with variable color that cause a banding pattern.
Occurrences
Amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks. Many of the hollow agates of southwestern Brazil and Uruguay contain a crop of amethyst crystals in the interior. Artigas, Uruguay and neighboring Brazilian state Rio Grande do Sul are large world producers exceeding in quantity Minas Gerais, as well as Mato Grosso, Espirito Santo, Bahia, and Ceará states, all amethyst producers of importance in Brazil.
It is also found and mined in South Korea. The largest opencast amethyst vein in the world is in Maissau, Lower Austria. Much fine amethyst comes from Russia, especially from near Mursinka in the Ekaterinburg district, where it occurs in drusy cavities in granitic rocks. Many localities in south India yield amethyst. One of the largest global amethyst producers is Zambia in southern Africa with an annual production of about 1000 tones.
Geological Properties Of Amethyst
Amethyst occurs at many localities in the United States. Among these may be mentioned: the Mazatzal Mountain region in Gila and Maricopa Counties, Arizona; Red Feather Lakes, near Ft Collins, Colorado; Amethyst Mountain, Texas; Yellowstone National Park; Delaware County, Pennsylvania; Haywood County, North Carolina; Deer Hill and Stow, Maine and in the Lake Superior region of Minnesota, Wisconsin and Michigan. Amethyst is relatively common in the Canadian provinces of Ontario and Nova Scotia. The largest amethyst mine in North America is located in Thunder Bay, Ontario.
Amethyst types
Purple Amethyst
Purple Amethyst has been highly esteemed throughout the ages for its stunning beauty and legendary powers to stimulate, and soothe, the mind and emotions. It is a semi-precious stone in today’s classifications, but to the ancients it was a “Gem of Fire,” a Precious Stone worth, at times in history, as much as a Diamond. It has always been associated with February, the month the Romans dedicated to Neptune, their water-god, and is the traditional birthstone of that month. It is the stone of St. Valentine and faithful love, and signifies ecclesiastical dignity as the Bishop’s Stone. It carries the energy of fire and passion, creativity and spirituality, yet bears the logic of temperance and sobriety.
Brandberg Amethyst
Brandberg Amethyst is a unique and extraordinary blend of Amethyst, Clear and Smoky Quartz together in one exceedingly high-vibrational crystal. It is found only in Namibia, Africa, and is imbued with remarkable phantoms, enhydros, and other rare formations and inclusions. It attunes to pure consciousness and is a potent talisman of healing and perfection with the capacity to restore one back to their etheric blueprint in order to realign with the Divine Source.
Chevron Amethyst
Chevron Amethyst displays v-shaped chevrons of deep purple and white Quartz that “seep” into beautiful layers. It is one of the finest Third-Eye stones for stimulating vision within the self as well as the physical world, filtering the life force from the cosmos via the Crown in its white layers and opening up spiritual and psychic channels through the purple. It has a strong, focused energy for dissipating and repelling negativity, and is the perfect crystal for learning any form of spiritual healing. Hold one in each hand for powerful but safe out-of-body travel, shamanic journeying or pathworking, and between the hands while praying or reciting mantras.
Cacoxenite in Amethyst
Cacoxenite in Amethyst mingles dark brown to yellow tufts of Cacoxenite, a phosphate mineral and major component in the Super Seven crystal, with the host crystal Amethyst. This combination brings a high level of creativity and new ideas to humanity by fostering thoughts that have never been thought of before. It is a calming stone, good in times of upheaval, and raises spiritual awareness of the creator essence in the beauty of nature and the kindness in people. Carry on the night of the crescent and full moon to transfer healing energy to the Earth and create an ethereal connection between all of the universe.
Rutiliated Amethyst
“Rutilated” Amethyst is a rare form of Amethyst which appears to contain Rutile, but actually contains brownish crystals of Goethite, an iron hydroxide mineral also found in the Super Seven crystal. Goethite is a stone for finding the link between the deep self and Earth, and together with Amethyst clears the Earth and Base Chakras, aligning the whole chakra system to the higher mind. It purifies the emotional body and is particularly helpful in grief work. It facilitates clairaudience, communion with angels, and connections with other worlds. To program as a wishing stone or with intentions, messages, and prayers, simply hold the stone with the intent in mind.
Physical properties of Amethyst
Chemical Formula: SiO2
Color: Purple
Hardness: 7
Crystal System: Hexagonal
Refractive Index: 1.54 – 1.55
SG: 2.63 – 2.65
Transparency: Transparent to translucent
Double Refraction: .009
Luster: Vitreous
Cleavage: Indiscernible
Mineral Class: Quartz
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