Birthstone by Zodiac
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Traditional Birthstone Calendar Month Genuine Cabochon Stone Genuine Faceted Stone January Garnet Garnet February Amethyst Amethyst March Bloodstone Aquamarine April Pearl or Mother-of-Pearl Diamond May Green Onyx Emerald June Moonstone Alexandrite or Pearl July Jasper Ruby August Carnelian Peridot September Lapis Lazuli Blue Sapphire October Opal Tourmaline (pink) November Citrine Citrine or Topaz (golden) December Turquoise Zircon or Tourmaline (blue) Gemstones of the Zodiac Sign Dates Stone Aquarius January 21–February 21 Garnet Pisces February 22–March 21 Amethyst Aries March 22–April 20 Bloodstone Taurus April 21–May 21 Sapphire Gemini May 22–June 21 Agate Cancer June 22–July 22 Emerald Leo July 23–August 22 Onyx Virgo August 23–September 22 Carnelian Libra September 23–October 23 Peridot Scorpio October 24–November 21 Beryl Sagittarius November 22–December 21 Topaz Capricorn December 22–January 20 Ruby Stone List Amethyst General Category Mineral variety Chemical Silica (silicon dioxide, SiO2) formula Identification Color Purple, violet Crystal habit 6-sided prism ending in 6- sided pyramid (typical) Crystal system rhombohedral class 32 Specific gravity 2.65 constant; variable in impure varieties Twinning Dauphine law, Brazil law, and Optical properties Uniaxial (+) Japan law Cleavage None Refractive index nω = 1.543–1.553 nε = 1.552–1.554 Fracture Conchoidal Birefringence +0.009 (B-G interval) Mohs 7–lower in impure varieties Pleochroism None scalehardness Luster Vitreous/glossy Melting point 1650±75 °C Streak White Solubility insoluble in common solvents Diaphaneity Transparent to translucent Other Piezoelectric characteristics Color The deep colors are the most valuable, particularly a rich purple with rose flashes. The "Siberian" deep purple with red and blue flash commands the highest prices. So-called green amethyst does not really count as amethyst, which is by definition violet or purple. Lighting In artificial light amethyst does not display its best color. It looks best in daylight, more precisely, particularly just after sunrise and before sunset, when the light is soft and warm. Clarity A fine amethyst is transparent, which means, the light passes through the stone unhindered. A translucent amethyst slightly weakens the passage of the light through the stone. The best quality amethyst is "clean", free of visible inclusions of any kind. As the amethyst is plentiful, there is little reason to buy stones with visible inclusions. Cut Due to the variability of the color distribution in the crystals, amethyst is often cut as brilliant round to maximize the color. Other cuts can be used when the color is better distributed. Amethyst is available in a wide range of calibrated sizes and shapes, including many fancy shapes. Amethyst location and deposits The most important deposits are in Brazil, namely the "Palmeira" amethysts of Rio Grande do Sul and the "Maraba" amethysts of Para. Other deposits are found in Bolivia, Canada, India, Madagascar, Mexico, Myanmar (Burma), Namibia, Russia, Sri Lanka, United States (Arizona), Uruguay and Zambia Common Amethyst treatments Heat treatment of 878-1382 degrees F (470-750 degrees C) results in light yellow, red-brown, green or colorless varieties Amethyst is the birthstone for those who are born in February or for the Zodiacsign of Pisces. Alexandrite A type of crysoberyl ategory Mineral Chemical Beryllium aluminium oxide, formula BeAl2O4 Identification Color Various shades of green and yellow; brownish, reddish; rarely, blue Crystal habit slender prisms and tabular form, dimensions are thin in one direction. Crystal system Orthorhombic 2/m2/m2/m Twinning Contact and penetration twins common, often repeated forming rosette structures Cleavage [110] Distinct, [010] Imperfect Fracture Conchoidal to uneven Mohs 8.5 scalehardness Luster Vitreous Streak White Specific gravity 3.5 - 3.84 Refractive Biaxial (+) nα=1.745 nβ=1.748 index nγ=1.754 Pleochroism Strong in alexandrite Major varieties Alexandrite Color change; green to red Cymophane Chatoyant The mineral or gemstone chrysoberyl, not to be confused with beryl, is [1] an aluminate ofberyllium with the formula BeAl2O4. The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones. Chrysoberyl is the third- hardest frequently encountered natural gemstone and lies at 8.5 on the hardness scale, between corundum (9) and topaz (8).[2] An interesting feature of its crystals are the cyclic twins called trillings. These twinned crystals have a hexagonal appearance, but are the result of a triplet of twins with each "twin" oriented at 120o to its neighbors and taking up 120o of the cyclic trilling. If only two of the three possible twin orientations are present, a "V"- shaped twin results. Alexandrite is one of the rarest of all colored gemstones and is famed for its color change from green in daylight to red under incandescent light. Fine faceted alexandrite over 1 carat is more valuable than sapphire, ruby oremerald. Alexandrite is a strongly pleochroicgem that will exhibit emerald green, red and orange-yellow colors and tend to change color in artificial light compared to daylight. The color change from red to green is due to strong absorption of light in the yellow and blue portions of the spectrum. Typically,alexandrite has an emerald-green color in daylight but exhibits a raspberry-red color in incandescent light. According to a popular but probably apocryphal story, alexandrite was discovered by the Finnish mineralogist Nils Gustaf Nordenskjold, (1792 -1866) on the tsarevitch Alexander's sixteenth birthday on April 17, 1834 and named alexandrite in honor of the future Tsar Alexander II of Russia. It is apparently true that alexandrite was first identified (but not discovered) by Nordenskjold, but likely some years earlier, around 1831. It was Count Lev Alekseevich Perovskii (1792-1856) who named the gem alexandrite. Tsar Alexander the II Alexandrite is very rare because of its chemical composition. While it is a form of chrysoberyl, it has an extra trace elemement in addition to iron and titatnium. It is the presence of chromium that gives it the emerald- green hue in daylight. Alexandrite exhbiting chatoyancy or the cat's eye effect is known, but very rare. The original source of alexandrite in the Ural mountains in Russia has been worked out. An important alexandrite deposit was found in 1987 in Minas Gerais in Brazil, and other deposits are found in Burma, Madagascar, Sri Lanka, India(Andra Pradesh) and Tanzania. Alexandrite is rarely found in larger sizes. The largest cut alexandrite weighs 66 carats and is in the Smithsonian Institution in Washington, D.C. Almandite garnet Category Silicate mineral 2+ Chemical formula Fe 3Al2Si3O12 Identification Color reddish orange to red, slightly purplish red to reddish purple and usually dark in tone Cleavage none Fracture conchoidal [1] Mohs scalehardness 7 - 7.5 Luster greasy to vitreous Specific gravity 4.05 (+.25, -.12) [1] Polish luster vitreous to subadamantine [1] Optical properties Single refractive, and often anomalous double refractive [1] Refractive index 1.790 (+/- .030) [1] Birefringence none Pleochroism none Dispersion .024 [1] Ultravioletfluorescence inert Absorption spectra usually at 504, 520, and 573nm, may also have faint lines at 423, 460, 610 and 680-690nm [1] Introduction Almandine Garnet, or almandite garnet belongs to the large and varied mineral group of garnet. Garnet comes from the Latin word "granatus", which means grain, because many garnet deposits are small grains of red crystals in or on their host rock. The dark brownish or purplish red stone is popular for its excellent hardness (7.5 on the Mohs scale) and its brilliance due to its high refractive index. Garnet is the January birthstone. Almandine Garnet colors The color is a pure, dark brownish or purplish red. Its deep red color is due to the presence of iron. Buying Almandine Garnet Color Pure, deep red is the most desirable color. Lighting Clarity In general, almandine garnet is an eye clean gem. Almandine garnet sometimes has asbestos fiber inclusions. These will produce four-ray, rarely six-ray, star stones when properly cut. They are highly prized by collectors because of their rarity. Cut Very large crystals exist, but because of their dark tone, only small to medium sized gems are faceted. These are often cut slightly shallow, to let light pass through. Star stones are cut en cabochon. Almadine garnet is found in a full range of shapes, including round, oval, pear and trillion. Almandine Garnet location and deposits Almandine Garnets are found in Brazil, India, Madagascar, Sri Lanka and the United States. Smaller deposits exist in Austria and the Czech Republic. Almandine garnet star-stones are found in India and the United States (Idaho). Common Almandine Garnet treatments Like most garnet the Almandine Garnet is not artificially enhanced in any way Amazonite troduction Amazonite is a gemstone variety of green microcline, a feldspar mineral. It is named after the Amazon river in Brazil. Surprisingly, no deposits of it have been found there. The name may refer to the variable green shades of the rainforest along the big river that are reflected in the gemstone. Amazonite, is usually cut encabochon, with a rounded and convex polished surface. In fact a fine quality amazonite can be mistaken for precious jade. Like jade, Amazonite is often carvedas well. Amazonite does not undergo any kind of treatment. Its relative softness of 6-6.5 on the Mohs scale makes Amazonite vulnerable to pressure and scratches and requires some care. Amazonite, though not common, is still very affordable. Amazonite is said to calm one's emotions and soothe nerves, and to enhance creativity and the ability to express oneself. Perhaps the strongest recommendation of its metaphysical powers is that Amazonite is said to make your married life happier. Amazonite colors Amazonite color varies from green, yellow-green to blue-green.