Blog, Gem stones

Ruby

Ruby

 Ruby is the red variety of the mineral corundum, an oxide of aluminum. It has a purplish-bluish red to yellow-red color. The finest color of ruby is pure red with a hint of blue, which is called “pigeons blood.” The substance that provides the color in ruby is chromium, and in the case of brownish tones, iron is present as well. Only stones of the darker hues are generally considered to be ruby. Rubies often contain inclusions called “silk,” that are caused by needle-like crystals of rutile. These inclusions sometimes form in a certain way as to produce what is known as a “star rub.” The word ruby comes from the Latin word “ruber,” meaning red. In Sanskrit, ruby is known as ratnaraj, meaning “king of precious stones.
 Ruby crystallizes in the trigonal crystal system, but the habit varies with the variety and locality.  For instance, Burmese rubies typically contain rutile, calcite, apatite, olivine, sphene and spinel inclusions. Ruby crystals tend to be hexagonal prisms with tapering or flat ends. They occur in igneous and metamorphic rocks, or as water-worn pebbles in alluvial deposits. Gem-quality ruby is found in north-central Myanmar, where it occurs in bands of crystalline limestone; in gravels in Thailand with sapphires and spinels; and in the gem gravels of Sri Lanka, where they are called “illam” by the local population and are usually light red to raspberry-red.. The gem-quality Thai rubies have a slightly darker purplish red color but are “cleaner” stones overall, having less rutile needle inclusions and more luster than Burmese rubies. However, in recent years Thai ruby production has been declining.Ruby is a rough stone, it appears dull and greasy, but, when cut, the luster can approach that of a diamond. Ruby is the hardest mineral after the diamond.
However, ruby has no cleavage, but has certain preferred directions of parting. The cutting of the rubies occurs in the country where they are mined. It is usually cut to yield the greatest weight but not necessarily the best proportions. The highest quality rubies come from the Mogok area of Burma.
 Ruby has been misidentified for hundreds of years. A famous example is the Black Prince’s Ruby, now in the Imperial State Crown of England and part of the Crown Jewels since 1367. It was not until the 19th century that it was discovered to be a spinel. The word Natural Ruby Gemstones was applied to fine garnets as well; “Cape rubies,” “Australian rubies”, and “Arizona rubies” are all garnet. Red tourmaline, has been called “Siberian ruby,” and “balas ruby” is red spinel.
Rubies are faceted or cut en cabochon. Trapiche rubies are mainly sought after by collectors and consist of a wheel-like growth of several prismatic ruby crystals. When cut or ground flat, trapiche crystals have the appearance of a wheel with black spokes.

 Synthetically made rubies started to be made toward the end of the nineteenth century, using the flame fusion method. Soon they became the first gems to be produced in commercial quantities. Synthetic rubies came to replace the “jewel” rubies which were traditionally used as bearings in watches and precision instruments. A particular good synthetic ruby is produced in Mexico under the name of “Ramaura Rubies,” it is created by the J.O. Crystal Company.To the Burmese, a fine ruby was a talisman of good fortune; it had the power of invincibility.

In ancient times it was believed that the ruby banished sorrow, restrained lust, and resisted poison. In Russia it is still believed that the ruby is good as a healing medicine for the heart, brain, vitality, and for clearing the blood. One of the world’s great star rubies, the 100.3 carat De long Star Ruby was discovered in Burma (now Myanmar) in the 1930s, and donated to the American Museum of Natural History in 1938. In 1964 it was stolen. The thieves were caught and the De Long Star Ruby was recovered after the payment of a $25,000 ransom. Ruby is one of the twelve gemstones of the ceremonial breastplate worn by the high priest Aaron, representing the twelve tribes of Israel as described in the Old Testament book of Exodus, and is also known as the month of birthstone meaning, happiness.

Ruby can be confused with almadite, pyrope, spinel, topaz, tourmaline, and zircon.

Blog, Jewels

Celestine

Celestine

Celestine is named after the Latin word caelestis, meaning “heavenly.”  It is a mineral consisting of strontium sulfate. The mineral is named for its occasional delicate blue color. Celestine occurs as crystals, and also in compact massive and fibrous forms. It is mostly found in sedimentary rocks, and often associated with the minerals gypsum, anhydrite, and halite.

Celestine is also known as celestite.  It is a transparent to translucent mineral.  It is found on sedimentary rocks, like limestones.  Celestine is used in fireworks, as an additive to battery lead and in the manufacture of rubber and paint.  It is also used in the nuclear industry, in sugar beet refining, and in the preparation of iridescent glass and porcelain. The most attractive crystals are pale sky blue, but colorless celestine is also common.  Its perfect cleavage makes it very fragile, but it is cut for the collector. Faceted crystal comes from Majunga, Madagascar.
Best celestine crystals are found in Lake Erie (United States), Bristol (England) and Sicily (Italy), also in Madagascar, Mexico and Canada.   It is mined in England, Russia and Tunisia
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Chrysocolla

Chrysocolla

Chrysocolla is a basic copper silicate composed of a mix of various microscopic crystals found in a variety of colors.  It has a greasy vitreous luster.  The name chrysocolla originated in ancient times, and was applied by the Greek philosopher Theophrastus in 315 BC to various materials used in soldering gold.  The name is derived from the Greek chrysos, meaning gold, and kolla, meaning glue.  It is a minor ore of copper and is used as an ornamental stone.

 Chrysocolla is harder than turquoise and softer than chalcedony. It is a secondary mineral and usually forms in the zone of alteration in all types of hydrothermal replacement deposits, where it is frequently associated with azurite, malachite and limonite. Chrysocolla is soft and fragile and tends to break easily when exposed to the atmosphere. It is mixed with quartz or chalcedony to give it durability.
Chrysocolla is frequently inter-grown with other minerals such as quartz, chalcedony, or opal to yield a harder, more resilient gemstone variety.  Inter-grown with turquoise and malachite from Israel it is called “Eilat stone,” which is the national stone of Israel. In 1950, the United States’ lapidaries voted chrysocolla-colored chalcedony the “most popular American gem.”
Most chrysocolla comes from the southwest United States, but it is also found at Cornwall, Lebanon Co., Pennsylvania. Fine specimens of glassy green chrysocolla were also obtained from copper mines at Bisbee, Cochise Co., in the Globe district, Gila Co., and in the Clifton-Morenci district, Greenlee Co., all in Arizona.
Chrysocolla is usually confused with azurite, dyed chalcedony, malachite, turquoise, and variscite.

 

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Chalcedony

Chalcedony

Chalcedony is a variety of microcrystalline quartz (silicon dioxide), often with some iron and aluminum.  It is composed of microscopic fibers.  Chalcedony is found in veins, geodes, and concretions.  It can be mammillary, botroyoidal, or stalactitic.  Chalcedony is found in numerous locations throughout the world.

 Its name may derive from the ancient port of
Its name may derive from the ancient port of Khalkedon in Asia Minor known today as (Turkey).
The word Chalcedony covers a group of quartzes, including agate, petrified wood, chrysophrase, bloodstone, jasper, carnelian, moss agate, and sard.  When pure, chalcedony has its own distinct properties.  It is translucent and has a white or bluish color, but it may be colored green by chromium. Chalcedony is formed in several environments, generally near the surface of the earth where temperatures and pressures are relatively low.
Apple-green chalcedony is called chrysoprase; dark red or orange-red to reddish brown chalcedony is called carnelian; dark green spotted with red inclusions is called heliotrope (bloodstone); distinctly banded specimens, in which adjacent bands differ in color and in degree of translucency, are called agate; and mottled yellow, red, brown, or green chalcedony is called jasper.
Good quality chalcedony is found in Brazil, India, Madagascar and Uruguay.  Its fibrous structure gives chalcedony its toughness and makes it ideal for carving, especially in Germany where it is very popular.  Because of its porous , it may be dyed with a variety of metallic salts.
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Cat’s Eyes

Cat's Eyes

 Cat’s eye is also known as “chrysoberyl cat’s eye,” or cymophane, from the Greek – waving light.  All other cat’s eye is designated with a different name.  Cat’s eye forms fine parallel inclusions that produce a silver-white line that appears as a moving light ray in a cabochon cut stone; resembling the pupil of a cat.  The most valuable examples of cymophane or cat’s-eye tend to show a thinner line of light. It is most prized when golden yellow-brown.

Cat’s-eye occurs in granitic rocks and pegmatites, and in mica schists. It is also frequently found in alluvial sands and gravels. Chrystoberyl cat’s eyes are not to be confused with quartz cat’s-eyes; they are greenish yellow, or yellow, often with a cold, grayish tone. Other stones showing chatoyancy should be called “tourmaline cat’s-eye, “ruby cat’s-eye and so forth. In ancient times Hindus believed that a cat’s eye guarded its owner’s health and provided assurance against poverty.

Deposits of chrysoberyl cat’s eye are found in the Ural Mountains of Russia, Sri Lanka and Brazil, as well as in China, southern India, and Zimbabwe. It is found in the United States but there are no major sources.

It is often confused with quartz cat’s eye, and prehnite cat’s eye.  Synthetic chrysoberyl cat’s eye and doublets are also known.

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Carnelian

Carnelian

Carnelian is a brownish red to orange, translucent to opaque chalcedony variety. The coloring agent is iron. Similar to carnelian is sard, which is generally harder and darker.  It is probably named after the color of the kornel cherry because of its color.  Its name comes from the Latin word carneus, which means “fleshy” also a reference to its color. The color of carnelian can be enhanced by heating.

 

 Carnelian is also known as cornelian.  It was once thought to still the blood and calm the temper.  It was also believed to give the owner courage in battle, and help timid speakers to be eloquent.  The ancient Greeks and Romans valued carnelian and used it for intaglios. It has also long been popular for signet rings. The Romans believed that dark carnelian represented the male; while the light color symbolized the female.
Fine quality carnelian may be found in Scotland, Brazil, and Washington State.  It is also found in Egypt, India, Scotland, Germany, Japan, Colombia the United States and China.

In India, when freshly mined, carnelian is often placed in the sun to change its brown tints to red.  Most carnelians in the market today are agates which are dyed and then heat-treated.  When held against the light, the color variety shows stripes; natural carnelian shows a cloudy distribution of color