Amber is fossil tree resin, which is appreciated for its color and beauty. Although not mineralized, it is often classified as a gemstone.
A common misconception is that amber is made of tree sap; it is not. Sap is the fluid that circulates through a plant's vascular system, while resin is the semi-solid amorphous organic substance secreted in pockets and canals through epithelial cells of the plant.
Because it used to be soft and sticky tree resin, amber can sometimes contain insects and even small vertebrates.
Amber occurs in a range of different colors. As well as the usual yellow-orange-brown that is associated with the color "amber", amber itself can range from a whitish color through a pale lemon yellow, to brown and almost black. Other more uncommon colors include red amber (sometimes known as "cherry amber"), green amber, and even blue amber, which is rare and highly sought after.
A lot of the most highly-prized amber is transparent, in contrast to the very common cloudy amber and opaque amber. Opaque amber contains numerous minute bubbles. This kind of amber is known as "bastard amber", even though it is in fact true amber.
Moonstone is typically a potassium aluminium silicate.
The most common moonstone is of the mineral adularia. The plagioclase feldspar oligoclase also produces moonstone specimens. Its name is derived from a visual effect, or sheen, caused by light reflecting internally in the moonstone from layer inclusion of different feldspars.
Moonstone's delicate beauty and its long heritage make it perhaps the most familiar gem quality member of the feldspar group. Moonstone is composed of two feldspar species, orthoclase and albite. The two species are intermingled. Then, as the newly formed mineral cools, the intergrowth of orthoclase and albite separates into stacked, alternating layers. When light falls between these thin, flat layers, it scatters in many directions producing the phenomenon called adularescence.
Deposits of moonstone are found in many countries and places: the European Alps; Brazil; India; Mexico; Myanmar; Madagascar; Sri Lanka; the USA, specifically Pennsylvania and Virginia; and Tanzania. However, it is Sri Lanka that produces the highest quality moonstones.
Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. It is rare and valuable in finer grades and has been prized as a gem and ornamental stone for thousands of years owing to its unique hue. In recent times turquoise, like most other opaque gems, has been devalued by the introduction of treatments, imitations, and synthetics onto the market, some difficult to detect even by experts.
The substance has been known by many names, but the word turquoise was derived around 16th century from the French language either from the word for Turkish (Turquois) or dark-blue stone (pierre turquin).<Actinic:Variable Name = '4'/> This may have arisen from a misconception: turquoise does not occur in Turkey but was traded at Turkish bazaars to Venetian merchants who brought it to Europe.<Actinic:Variable Name = '4'/> The colour, however, has been employed extensively in the decorative tiles adorning Turkish places of worship and homes for hundreds of years, beginning with the Seljuks, or was derived from the colour of the Mediterranean Sea on the southern Turkish coast and the association quite possibly has caused the name to take root.
Labradorite ((Ca,Na)(Al,Si)4O8), a feldspar mineral, is an intermediate to calcic member of the plagioclase series.
The geological type area for labradorite is Paul's Island near the town of Nain in Labrador, Canada. It occurs in large crystal masses in anorthosite and shows an iridescence or play of colors.
Gemstone varieties of labradorite exhibiting a high degree of iridescence are called spectrolite; moonstone and sunstone are also commonly used terms, and high-quality samples with good iridescent qualities are desired for jewelry.
Amethyst is a violet variety of quartz often used in jewelry. The name comes from the Ancient Greek a- '(not') and methustos ('intoxicated'), a reference to the belief that the stone protected its owner from drunkenness; the ancient Greeks and Romans wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication.
Amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks. It is also found and mined in South Korea. The largest opencast amethyst vein in the world is in Maissau, Lower Austria. Many of the hollow agates of Brazil and Uruguay contain a crop of amethyst crystals in the interior. 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 India yield amethyst. One of the largest global amethyst producers is Zambia with an annual production of about 1,000 t.
Citrine is a variety of quartz whose color ranges from a pale yellow to brown. It is nearly impossible to tell cut citrine from yellow topaz visibly. Citrine has ferric impurities, and is rarely found naturally. Most commercial citrine is in fact artificially heated amethyst or smoky quartz. Brazil is the leading producer of citrine, with much of its production coming from the state of Rio Grande do Sul.
Citrine is one of three traditional birthstones for the month of November
Rose quartz is a type of quartz which exhibits a pale pink to rose red hue. The color is usually considered as due to trace amounts of titanium, iron, or manganese, in the massive material. Some rose quartz contains microscopic rutile needles which produces an asterism in transmitted light. Recent X-ray diffraction studies suggest that the color is due to thin microscopic fibers of possibly dumortierite within the massive quartz.
In crystal form (rarely found) it is called pink quartz and its color is thought to be caused by trace amounts of phosphate or aluminium. The color in crystals is apparently photosensitive and subject to fading. The first crystals were found in a pegmatite found near Rumford, Maine, USA, but most crystals on the market come from Minas Gerais, Brazil.
Rose quartz is not popular as a gem. The mineral is generally too clouded by impurities but very rarely suitable. Rose quartz is more often carved into figures such as people or hearts. Hearts are commonly found because rose quartz is pink and an affordable mineral.
Peridot is gem-quality forsteritic olivine.
The origin of the name "peridot" is uncertain. The Oxford English Dictionary suggests an alteration of Anglo-Norman pedoretés (classical Latin paederot-), a kind of opal, rather than the Arabic word faridat, meaning "gem".
Olivine in general is a very abundant mineral, but gem quality peridot is rather rare.
Peridot is one of the few gemstones that occur in only one color: basically an olive green. The intensity and tint of the green however depends on how much iron is contained in the crystal structure, so the color of individual peridot gems can vary from yellow-green through olive green to brownish green. The most valuable is considered a dark-olive green color.
Peridot crystals have been collected from some Pallasite meteorites. A famous Pallasite was offered for auction in April 2008 with a requested price of close to $ 3 million at Bonhams, but remained unsold. Peridot is the only gemstone found in meteorites.
Peridot olivine is the birthstone for August. It is sometimes mistaken for emeralds and other green gems.
Lapis lazuli (pronounced lap-is-la-zyoo-lie or lee) (sometimes abbreviated to lapis) is a semi-precious stone prized since antiquity for its intense blue color.
Lapis lazuli has been mined in the Badakhshan province of Afghanistan for 6,500 years, and trade in the stone is ancient enough for lapis jewelry to have been found at Predynastic Egyptian sites, and lapis beads at neolithic burials in Mehrgarh, the Caucasus, and even as far from Afghanistan as Mauritania.
Lapis lazuli is a rock, not a mineral: whereas a mineral has only one constituent, lapis lazuli is formed from more than one mineral.
The main component of lapis lazuli is lazurite (25% to 40%), a feldspathoid silicate mineral composed of sodium, aluminium, silicon, oxygen, sulfur, and chloride. Most lapis lazuli also contains calcite (white), sodalite (blue) and pyrite (metallic yellow). Other possible constituents are augite, diopside, enstatite, mica, hauynite, hornblende and nosean. Some contain trace amounts of the sulfur rich lollingite variety geyerite.
The finest color is intense blue, lightly dusted with small flecks of golden pyrite. Stones with no white calcite veins and only small pyrite inclusions are more prized. Patches of pyrite are an important help in identifying the stone as genuine and do not detract from its value. Often, inferior lapis is dyed to improve its color, producing a very dark blue with a noticeable grey cast which may also appear as a milky shade.
Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate.
As the transparent variety iolite, it is often used as a gemstone. The name "iolite" comes from the Greek word for violet. Another old name is dichroite, a Greek word meaning "two-colored rock", a reference to cordierite's strong pleochroism. It has also been called "water-sapphire" and "Vikings' Compass", because of its ability to determine the direction of the sun on overcast days. This works by determining the direction of polarization of the sky overhead. Light scattered by air molecules is polarized, and the direction of the polarization is at right angles to a line to the sun, even when the sun's disk itself is obscured by dense fog or lies just below the horizon. Gem quality iolite varies in color from sapphire blue to blue violet to yellowish gray to light blue as the light angle changes.
Iolite is sometimes used as an inexpensive substitute for sapphire. It has a low price tag because it is much softer than sapphires and is abundantly found in Sri Lanka, India, Burma, Australia's Northern Territory, Namibia, Brazil, Tanzania, Madagascar, Connecticut, and the Yellowknife area of the Northwest Territories of Canada.
Charoite is a rare mineral, named for the Chara River (though this etymology is disputed by some), and found only in the Sakha Republic, Siberia, Russia. It is found where a syenite massif has intruded into and altered limestone deposits.
Charoite is a strong, translucent lavender to purple in color, reminding some of a granite or marble with its pearly, swirling luster. However, it is a discrete mineral rather than a rock. Charoite is strictly massive in nature, and fractures are conchoidal. It has an unusual swirling, fibrous appearance, sometimes chatoyant, and that, along with its intense color, sometimes of a "grape" nature, can lead many to believe at first that it is synthetic or enhanced artificially.
Though reportedly discovered in the 1940s, it was not known to the outside world until its description in 1978. It is said to be opaque and unattractive when found in the field, a fact that may have contributed to its late recognition. Charoite is used as an ornamental stone and sometimes a gemstone, generally as cabochons set into pendants.
Russia has fairly strict prohibitions on the exportation of charoite. Generally, charoite is permitted to be exported only after the stone has been worked, for example, into figurines or other type ornaments. It is therefore difficult to procure "unworked" or "rough" charoite in a form suitable for further working into jewelry such as cabochons.
Charoite often contains inclusions of the mineral tinaksite, which appears as a golden, spire-like shape running through the material.
Mother of Pearl
Nacre, also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer. It is strong, resilient, and iridescent.
This substance is called "mother of pearl" because it is literally the "mother", or creator, of true pearls.
Nacre is found in certain ancient lineages of bivalves, gastropods and cephalopods. However, the inner-shell layer in the great majority of shelled mollusks is porcellaneous and non-nacreous, frequently resulting in a non-iridescent shine like that of a porcelain plate or, in some species, presenting non-nacreous iridescent effects such as 'flame structure' (e.g. conch pearl).
Pearls and the inside layer of pearl oyster shells and freshwater pearl mussel shells are made of nacre.
Nacre is secreted by the epithelial cells of the mantle tissue of some species of mollusk. The nacre is continuously deposited onto the inner surface of the shell, the iridescent nacreous layer, commonly known as mother of pearl. The layers of nacre smooth the shell surface and help defend the soft tissues against parasites and damaging detritus by entombing them in successive layers of nacre, forming either a blister pearl attached to the interior of the shell, or a free pearl within the mantle tissues. The process is called is encystation and it continues as long as the mollusk lives.
Chief sources of mother of pearl are the pearl oyster, found in warm and tropical seas, primarily in Asia; freshwater pearl mussels, which live in many rivers of the United States, Europe, and Asia; and the abalone of California, Japan, other Pacific regions and of the Indian Ocean off Southern Africa. Also widely used for pearl buttons, especially during the 20th century, is the shell of the great green turban snail, Turbo (Lunatica) marmoratus
Technically, chalcedony is any form of microcrystalline or cryptocrystalline quartz, meaning any form of quartz whose crystals are too small to be seen without high magnification. In common practice, only the translucent, single color types are sold as "chalcedony", whereas the rest of this group is sold under individual variety names, such as agate, carnelian, bloodstone, jasper or onyx. Chalcedony is named after the ancient seaport of Chalcedon (Kardikoy, Turkey).
Blue chalcedony, called "Mohave" and "Mt. Airy Blues", originating in California and Nevada, are slightly to moderately grayish blue with a light to medium color range. Blue chalcedony from Namibia, often called "African Blue", varies from grayish to nearly pure blue and from light to medium dark. The most unusual and most valuable type is from Oregon. Its blues are modified by slight to moderate amounts of pink, making a noticeably lavender gem, which nonetheless is called "Holly Blue."
Chrysoprase, apple green chalcedony that derives its color from nickel, ranges from nearly opaque to nearly transparent. Its color spectrum includes olivey, to nearly pure greens of medium tone. Very fine, highly saturated pieces have been successfully misrepresented as Imperial jade.
Tiger's eye (also called Tigers eye or Tiger eye) is a chatoyant gemstone that is usually a metamorphic rock that is yellow- to red-brown, with a silky luster. A member of the quartz group, it is a classic example of pseudomorphous replacement by silica of fibrous crocidolite (blue asbestos). An incompletely silicified blue variant is called Hawk's eye.
The gems are usually cut en cabochon in order to best display their chatoyancy. Red stones are brought about through gentle heat treatment. Honey-coloured stones have been used to imitate the much higher valued cat's eye chrysoberyl (cymophane), but the overall effect is unconvincing. Artificial fiberoptic glass is a common imitation of tiger's eye, and is produced in a wide range of colors. Tiger's Eye mostly comes from South Africa.
Tiger iron is an altered rock composed chiefly of tiger's eye, red jasper, and black hematite. The undulating, contrasting bands of colour and luster make for an attractive motif, and it is mainly used for jewelry-making and ornamentation. Tiger iron is a popular ornamental material used in a variety of applications, from beads and cabochons to knife hilts. Along with tiger's eye it is mined primarily in South Africa and Western Australia.
Malachite often results from weathering of copper ores and is often found together with azurite, goethite, and calcite. Except for its vibrant green color, the properties of malachite are similar to those of azurite and aggregates of the two minerals occur frequently together. Malachite is more common than azurite and is typically associated with copper deposits around limestones, the source of the carbonate.
Large quantities of malachite have been mined in the Urals. It is found in the Democratic Republic of Congo; Zambia; Tsumeb, Namibia; Ural mountains, Russia; Mexico; Broken Hill, New South Wales; England; Lyon; and in the Southwestern United States especially in Arkansas and Arizona. In Israel, malachite is extensively mined at Timna valley, often called King Solomon's Mines although research has shown that the site was not in use during the 10th century. Archeological evidence indicates that the mineral has been mined and smelted at the site for over 3,000 years. Most of Timna's current production is also smelted, but the finest pieces are worked into silver jewelry.
In Greek mythology, the throne of Demeter, goddess of grain and harvest, was fashioned from malachite and adorned with golden pigs and ears of barley.