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Kyanite

Kyanite

Kyanite

Kyanite’s name derives from the Greek kyanos, meaning “dark blue.” It occurs in metamorphic rocks such as schist and gneiss associated with garnet, staurolite and micas; and in eclogites. The presence of kyanite in rocks indicates that they have undergone moderate temperatures and medium to high pressures during metamorphism. Associated minerals include andalusite, corundum, and staurolite.

 

Kyanite has a vitreous luster, often with irregular streaks. It is difficult to cut because of its variable hardness and cleavage. This variable in hardness is also known as disthene; meaning “double strength,” after the hardness, which is greater across the crystal than lengthwise.

 

The colors of gem-quality kyanite are shades of blue, white, green, gray and occasionally black. It is transparent to translucent and the luster ranges from vitreous to pearly. In jewelry a great deal of bead and cabochon material contains inclusions of quartz, pyrite crystals, hematite flakes and fibers of ilmenite and rutile. It makes a rather brittle gemstone that is susceptible to splitting. It requires careful handling, so any polishing should be done at low speed and ultrasonic and chemical cleaners should not be used. However, it is not sensitive to heat.

 

Kianite can be found in Bahia, Brazil; the St. Gotthard region of Switzerland; Urals in Russia; and Yancy County, North Carolina

 

Kyanite can be confused with aquamarine, benitoite, iolite, dumortierite, and tourmaline; and very often with sapphire.

Jet

Jet

Jet

Jet is a hard gem variety of lignite (a type of coal), which is often carved or faceted, and takes a good polish. Jet has high carbon content and a layered structure. It is black to dark brown, and sometimes contains tiny inclusions of pyrite, which have a metallic luster. Jet’s name derives from the Old French jyet or jaiet after a place on the Mediterranean coast where the Romans obtained some of their jet. Jet is the fossilized wood of prehistoric trees that have been compressed over millions of years. It smells like coal when burnt. Some jet may induce electricity when rubbed, and for this reason it is sometimes known as “black amber.”

Jet was a very popular gemstone during the Victorian era when it was used as mourning jewelry. After the death of Queen Victoria’s husband, Prince Albert in 1861, Queen Victoria went into a forty year period of mourning. Jet from Whitby in northern England was used extensively. Whitby was famous at the time for the mining and crafting of jet, and this industry was responsible for most of town‘s income during that time. Jet has been used in jewelry since ancient times and was made traditionally into rosaries for monks. In medieval times, powdered jet drunk in water or wine was believed to have medicinal properties. In India, jet amulets were believed to protect the wearer against the evil eye, and Irish women traditionally burned jet to ensure the safety of their husbands when away from home.

Today jet is found in Whitby, England, Spain, France, Germany, Poland, India, Turkey, Russia, and the United States.

Jet can be confused with anthracite, asphalt, cannel coal, onyx, and schorl. Some imitations are made with glass, vulcanite and plastics.

Jasper

Jasper

Jasper

Jasper is usually considered as chalcedony.  Geologists sometimes put it in a group by itself within the quartz group because of its grainy structure.  The name jasper is derived from the Greek word “iaspis, which means “spotted stone.”  It incorporates various amounts of materials that give it both its opacity and color.  Brick-red to brownish-red jasper contains hematite; clay gives rise to a yellowish-white or gray, and goethite produces brown or yellow.  Jasper is formed through deposition from low-temperature, silicarich waters percolating through cracks and fissures in other rocks, incorporating a variety of materials in the process.

 

Jasper has been used for jewelry and ornamentation since Paleolithic times.  The Babylonians believed that jasper influenced women’s diseases, and was a symbol of childbirth.  The 11th-century Bishop of Rouen, Marbodius, stated that jasper “placed on the belly of a woman in childbirth, relieves her pangs.”  This comes from a time when all stones were believed to be alive and have a sex, jasper being a female stone.

 

Uniformly colored jasper is rare; usually it is multicolored, striped, or flamed.  Sometimes jasper can be grown together with agate or opal.  There is also fossilized material.  It occurs as fillings of crevices or fissures or in nodules.
It is used for ornamental objects, cabochons, and for stone mosaics.

 

There are many names of jasper used in the trade:  Agate jasper (yellow, brown, or green blended, grown together with agate); Egyptian jasper (Nile pebble) strongly yellow and red; Banded jasper (layered structure with more or less wide bands); Basanite (fine-grained, black.  It is used by jewelers and goldsmiths for streak-tests of precious metals); Blood jasper (name sometimes used for bloodstone); Hornstone (very fine grained, gray, brown-red, more rarely green or black.  Sometimes hornstone is understood as a general synonym for jasper); Scenic jasper (brown marking, caused by iron oxide, resembling a landscape); Moukaite (pink to light red, cloudy.  Found in Australia); Nunkirchner jasper (whitish gray, rarely yellow or brownish-red – named after deposits in Rhineland-Palatine), dyed with Berliner blue, misleadingly called “German lapis” or “Swiss lapis” in imitation of lapis lazuli; Plasma (dark green, sometimes with white or yellow spots; and Silex (yellow and brown-red spotted or striped).

 

Deposits of jasper are found in Egypt, Australia, Brazil, India, Canada, Kazakhstan, Madagascar, Russia, Uruguay, and the United States.

Jadeite

Jadeite
Jadeite

There are two different minerals known as jade.  They are “nephrite,” which is an amphibole, and “jadeite,” which is a pyroxene.  Nephrite is the most common and widespread.  It is formed of a mat of tightly interlocking fibers, creating a stone tougher than steel.  It was used in China and New Zealand for tools and weapons due to its toughness.  Its color varies with its composition dark green when iron-rich; cream colored when magnesium-rich.  The term “jade” evolved from the Spanish piedra de ijada, meaning “loin stone,” a stone of similar appearance to nephrite brought from the New World by the Spanish, which was, in fact, jadeite.

There are two different textures that help distinguish nephrite from jadeite; nephrite appears fibrous or silky; jadeite commonly has a more sugary or granular texture.  It has a bright glassy shine.  Pure jadeite is white.  Its other colors include green, colored by iron; lilac, colored by manganese and iron; and pink, brown, red, blue, black, orange, and yellow, colored by inclusions of other minerals.  Emerald-green jadeite, colored by chromium, is called imperial jade.  The latest classification of jadeite jade is; “A” jade (natural untreated); “B” jade (polymer treated); “C” jade (stained); “B” & “C” jade (polymer treated and stained).

For the Indians of Mexico, Central, and South America, jadeite was a symbol of water and the burgeoning of plant life. Known as chalchihuitil, it was more precious than gold.  The Olmecs were the first Mesoamericans to discover and carved jade; perhaps 3,000 years ago. Across Mexico and Central America it was used in the most precious objects: masks, depictions of the gods, and ritual items.  A piece of jade was placed in the mouth of a deceased nobleman which was believed to serve as his or her heart in the afterlife.  Jade grave goods were essential for members of the nobility in most Mesoamerican cultures.  When powdered and mixed with herbs, jadeite was used to treat fractured skulls and fevers, and to resurrect the dying.  Mesoamerican jadeite principally came from sources in Guatemala and Costa Rica.

Myanmar is a major source of jadeite, and in particular imperial jade.  Other sources are in Japan and California.  Until the late 16th century, virtually all European jade was nephrite.  When the Spanish reached Mexico, they discovered that the Aztecs prized a green stone that was similar in appearance to, and believed to be the same stone as, European jade.  They were told by the Aztecs that this stone cured internal ailments, especially those of the liver, spleen, and kidneys.  This stone was brought back to Europe, along with the belief in its healing powers.  The jade from South America was believed to be the same as the Old World jade until 1863, when a Chinese carving was analyzed and discovered to be a different stone.  The new stone was given the name jadeite, meaning derived from jade.

Jadeite and Nephrite can often be confused with agalmatolite, amazonite, aventurine, californite, chrysoprase, hydrogrossular garnet, pectolite, plasma, prase, prehnite, serpentine, emerald, smaragdite, smithsonite, and verdite

Howlite

Howlite

Howlite

Howlite was discovered in 1868 by a Nova Scotia chemist, geologist and mineralogist named Henry How. It is a calcium borosilicate hydroxide. It is usually white in color with veins of other minerals running through the nodules. They are easily distinguished by its inferior hardness – turquoise Moh’s hardness being 5-6 and Howlite – Moh’s hardness being 3.5.

Howlite develops in evaporate deposits and usually occurs with ulexite and colemanite as nodules in clay. Howlite has a white; subvitreous, glimmering, dull; streak white color and luster. A species very similar to Howlite is datolite which is harder than howlite and will not dissolve in hydrochloric acid. Howlite is easily fusible.

 

Howlite occurs with other boron minerals, such as kernite and borax, and is found in quantity in the Karamer district of Death Valley and San Bernardino County, California where you can find nodules sometimes several hundred pounds in weight, especially with colemanite at Lang, Los Angeles Co., and with ulexite near Daggett, San Bernardino Co.

Hematite

Hematite
Hematite

Hematite or haematite takes its name from the Greek word haem for “blood,” which describes the color of its powdered form. Hematite is the most important iron ore because of its high iron content (70 percent) and its abundance. The steel-gray crystals and coarse-grained varieties with a metallic luster are known as specular hematite; the thin scaly forms are micaceous hetatite; and the crystals in flower-like arrangements are called iron roses. Hematite is also found as an accessory mineral in many igneous rocks.

 

Much hematite is a soft, fine-grained, earthy form called red ocher, which is used as a pigment. Ancient Egyptians decorated the tombs of pharaohs, with powered hematite, as well as Native Americans that used it for war paint. Egyptians used it for amulets and the Babylonians believed that it would “procure for the wearer a favorable hearing of petitions addressed to kings and a fortunate issue of lawsuits and judgment”. Today it is still used as red ocher pigment and as a metal polishing powder called “jeweler’s rouge,” which is used to polish plate glass and jewelry, and was in the past used to polish gems. Black varieties of hematite were once used for mourning jewelry.

 

The most important hematite deposits are sedimentary in origin, either in sedimentary beds or metamorphosed sediments. Lake Superior in the United States is the world’s largest producer, but other major deposits are found in the Ukraine, China, India, Australia, Liberia, Brazil, and Venezuela. The best cuttable sources come from Cumbria, northwest England; Rhineland-Palatinate, Germany; and the island of Elba, Italy.