Hambergite, named after Axel Hamberg, the Swedish mineralogist, occurs as colourless to yellowish white crystals, but is rarely gem-quality. Brittle, with perfect cleavage, it's very fragile and suitable just for collectors. When cut, it appears like glass, but double images of the rear facets might be seen with the table facet because of its high birefringence.
Gem quality hambergite can be found in Kashmir (India), as well as in Madagascar.
Several types of gypsum are utilized as decorative stones. The most crucial, alabaster, is located as fine-grained masses in pastel shades, but is often stained in stronger colours. Selenite is colourless, occasionally cut for collectors, but very soft. Satin spar is really a fibrous variety, polished or cut “en cabochon”. Rose shapes (called "desert rose") also occur.
Localities include Italy and England (Alabaster), Italy, Mexico, the United States and Chile (Selenite).
Gem quality specimens of the mineral olivine are known as peridot by gemmologists. Peridot comes with an olive or bottle green colour because of the presence of iron, along with a distinctive oily or greasy lustre. It features a high birefringence, so doubling of the rear facets may be easily observed in larger specimens when viewed in the front. Good-quality crystals are extremely rare.
Peridot is the green variety of the Olivine Group of minerals. Olivine is not an individual mineral but a group of minerals that includes Fayalite, Forsterite, Liebenbergite, Tephroite and Laihunite. Fayalite (Mg2SiO4) is the iron rich member of the Fayalite - Forsterite mineral series, Forsterite (Fe2SiO4) is the magnesium rich member. Peridot (Mg2Fe2SiO4) is the green variety of Forsterite containing both Iron (Fe) and magnesium (Mg). Peridot's color can vary from pale to rich green (for which Peridot is famous) to brown. The considerable variation in shades of green to brown is dependant on locality of origin and amount of ferrous iron. The ideal green Peridot has an iron content of about 12-15%. More iron results in a muddy color. Very bright green Peridot may also contain traces of chromium.
Peridot is not a recognized mineral name. It's hard to believe that Peridot is the equivalent of a trade name, not a recognized mineral name since it is one of the most popular and well known gems in the world. Peridot has been a popular gem throughout history.
Peridot is available from many localities worldwide including these well known sources: Mogok, Sagaing District, Mandalay Division, Burma (Myanmar); St John's Island (Zagbargad; Zebirget; Topazios), Red Sea, Egypt; Naran-Kagan Valley, Kohistan District, North-West Frontier Province, Pakistan; and Peridot Mesa, San Carlos, San Carlos Indian Reservation, Gila Co., Arizona, USA
The attractive, bright green color of uvarovite is due to the presence of chromium. The crystals are very fragile, with subconchoidal to uneven fracture. Uvarovite occurs in serpentine rocks. The best clear crystals are found in the Urals in Russia, lining cavities or rock fissures. Other sources are Finland, Turkey, and Italy.
Gem-quality spessartite (also known as spessartine) is uncommon. It is bright orange when pure, but an increase in the iron content makes the stone darker orange to red. Inclusions are lace - or feather-like.Spessartite occurs in granitic pegmatites and alluvial deposits. It is found in Sri Lanka, Madagascar, Brazil, Sweden, Australia, Burma, and the USA; also Germany and Italy, but crystals there are too small to facet. Spessartine is named after Spessart district of Bavaria, Germany. It can be confused with hessonite garnet or yellow topaz, but on close examination of inclusions it is distinguishable.
The blood-red color of pyrope garnet is due to its iron and chromium content. It rarely has inclusions, but when present they are rounded crystals or have irregular outlines. As with all garnets, pyrope has no cleavage, and fracture is subconchoidal to uneven. Pyrope garnet is found in volcanic rock and alluvial deposits, and may, along with certain other minerals, indicate the presence of diamond-bearing rocks. Localities include Arizona (USA), South Africa, Argentina, Australia, Brazil, Burma, Scotland, Switzerland, and Tanzania. Pyrope comes from the Greek pyrops, meaning fiery. Swiss and South African pyropes are lighter red than stones from Bohemia, where pyrope jewelry has been made for over 500 years. Perfectly transparent, clear, uniformly colored crystals of pyrope garnet were popular for jewellery in the 18th and 19th centuries.
The possible admixtures among the garnet group species give rise to the following intermediate species which are known in the trade as Rhodolite, Malaya, Pyrandine, Pyralspite, etc. As there are varying percentages of isomorphous replacements, their properties show considerable variations. Pyrope - Almandine Garnet (Rhodolite): Color is basically purplish red, brownish red and violet-red, whose properties are as follows:
Pyrope - Spessartite Garnet (Color Changing): The color is bluish green in daylight and purplish red in lamplight. Some exhibit a purplish blue to purplish red color change.
Hessonite Garnet: It occur in a very wide range of colors, from colorless right through to black, but terive their name from the first specimen ever found, a distinctive gooseberry-green color. The orange-brown color of hessonite grossular garnet is due to manganese and iron inclusions. It has swirls of inclusions, giving it a treacly appearance. The best hessonite garnets are found in Sri Lanka in metamorphic rocks, or gem gravels and sands. In Madagascar hessonite is often referred to as cinnamon stone. Other localities include Brazil, Canada, and Siberia (Russia), as well as Maine, California, and New Hampshire in the USA. Both the Ancient Greeks and Romans made cameos, intaglios, and cabochons from hessonite, and faceted stones for jewelry. Green Grossular Garnet: There are two varieties of green grossular: one is found as transparent crystals, the other is massive. Massive green grossular from South Africa is called Transvaal jade, after its main locality and because it resembles jade. It may contain black specks of the mineral magnetite. Since the 1960s a transparent, green grossular garnet, named tsavorite, has been mined in Kenya. Massive green grossular is used as a decorative stone; tsavorite is faceted as a gem. Found in Canada, Sri Lanka, Pakistan, the former USSR, Tanzania, South Africa, and the USA. Kenya is the main source for tsavorite. The name "grossular" is derived from the botanical name of the gooseberry, R. grossularia. Massive grossular garnet of a gooseberry-green color was first discovered in the former USSR. Since then it has also been found in Hungary and Italy. Pink Grossular is found in Mexico, usually as a massive form in metamorphic rocks. Crystals are rare. It also occurs in South Africa. Pinkish grossular from Mexico may be known as rosolite.
Garnets containing titanium and manganese are grouped as andradite garnet. The most valuable is demantoid, whose emerald-green color is due to the presence of chromium. It has a higher dispersion than diamond and can be recognized by the characteristic "horsetails", which are fine, hair-like inclusions of asbestos. Topazolite, the yellow variety of andradite garnet, varies from pale to dark yellow. Only small crystals are found. Melanite is a generally black form, but can also be dark red. The best demantoid is found in the Urals in Russia, and is associated with gold-bearing sands and metamorphic rocks. Other localities include northern Italy, Zaire, and Kenya. Topazolite crystals are found in the Swiss and Italian Alps in metamorphic rocks. Melanite is found in metamorphic rocks and volcanic lavas; fine crystals are found on the island of Elba (Italy), and in France and Germany.
Did you know?
In Turkey, people fix a piece of amber in the hubble-bubble, dogged by an age old belief that the presence of the jewel would destroy all the germs and no disease would spread, even after many have dragged their puffs from it.
Almandine is generally darker red than pyrope and may appear black, although pinkish red specimens are found. It is usually opaque or sub translucent, but the rare transparent stones have high lustre. Although dense, almandine is brittle and facet edges chip. Many stones show characteristic inclusions and four-rayed stars may be seen when stones are cut in cabochon. Needle-like crystals of rutile or hornblende are typical inclusions in almandine. The darker almandines are frequently cut as cabochons or used as abrasives in garnet paper. The underside of dark almandine is often hollowed out to let more light filter through the stone. Almandine is found in metamorphic rocks, such as garnet mica schist, and less frequently in granitic pegmatites. It has a worldwide occurrence. Slices of garnet have been used in windows in churches and temples, and legend has it that Noah suspended garnet in the ark in order to disperse light. Garnet was once said to cure melancholy and to warm the heart.
Fuchsite(Verdite) is a variety of muscovite, a green color rock of chrome mica with chemical composition aluminium silicate. The green emerald color is due the high percentage of chromium and it is a good simulant for emerald. It is generally formed either in fibrous or massive form in pegmatite. The best known fuchsite comes from South Africa. Due to the low hardness of fuchsite 2.5 - 4, it is advised not to use it in day to day life as it can get scratch. Fuchsite is very familiar with ruby. Ruby - Zoisite is a stone where by ruby is naturally occurred within fuchsite better now known as ruby in fuchsite. This stone is extensively worn as beads and can be used in daily basis.
Fluorite is a semi precious stone sourced from U.S.A, Mexico, Germany, India, etc. The key identifying feature of this gemstone is its low R.I. (1.434) with high S.G. (3.18). Formerly called fluorspar, fluorite has limited use as a gemstone because it is relatively soft therefore easily scratched. However, the wide range of colors (including yellow, blue, pink, purple, and green), the frequent incidence of more than one color in a single specimen, and zoning or patchy distribution of color, make it an interesting stone. Despite its fragility and perfect octahedral cleavage, stones may be faceted (usually for collectors), and can be polished very brightly. Localities include Canada, the USA (where some of the largest crystals are found), South Africa, Thailand, Peru, Mexico, China, Poland, Hungary, Czechoslovakia, Norway, England, and Germany. Pink octahedral crystals are found in Switzerland. A purple and yellow banded variety called Blue John occurs in Derbyshire (England) which is mostly sought for collectors. Fluorite is soft and difficult to facet. It may be mistaken for glass, feldspar, beryl, or quartz. The Ancient Egyptians used fluorite in statues and to carve scarabs, and the Chinese have used it in carvings for more than 300 years. In the 18th century, fluorite was powdered in water to relieve the symptoms associated with kidney disease.
The yellow variety of orthoclase feldspar is generally faceted like a step-cut, since the stones in many cases are fragile. The yellow colour is a result of the existence of iron. Orthoclase crystals are columnar or tabular prisms, and therefore are often twinned.The very best yellow orthoclase can be found in Madagascar in pegmatites, and could be faceted for that collector. Yellow orthoclase from Madagascar and Germany may be slashed “en cabochon” to exhibit the cat’s eye effect. Feldspars form in igneous and metamorphic rocks. Which sort is created depends upon the temperature it forms at, and just how it cools.
