Lapis Lazuli
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.
Sources
The best lapis lazuli is found in limestone in the Kokcha river valley of Badakhshan province in northeastern Afghanistan, and these deposits in the mines of Sar-e-Sang have been worked for more than 6,000 years. Badakhshan was the source of lapis for the ancient Egyptian and Mesopotamian civilizations, as well as the later Greek and Roman; during the height of the Indus valley civilization about 2000 B.C., the Harappan colony now known as Shortugai was established near the lapis mines.
More recently, during the 1980s conflict with the USSR, Afghanistan resistance fighters disassembled unexploded Soviet landmines and ordnance and used the scavenged explosive to help mine lapis to further fund their resistance efforts.
In addition to the Afghan deposits, lapis has been extracted for years in the Andes near Ovalle, Chile, where the deep blue stones compete in quality with those from Afghanistan. Other less important sources include the Lake Baikal region of Russia, Siberia, Angola, Burma, Pakistan, USA (California and Colorado), Canada and India.
Malachite
Malachite is a carbonate mineral normally known as "copper carbonate" with the formula Cu2CO3(OH)2. This green-colored mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses. Individual crystals are rare but do occur as slender to acicular prisms. Pseudomorphs after more tabular or blocky azurite crystals also occur.
Occurrence and historical uses
Malachite often results from weathering of copper ores and is often found together with azurite (Cu3(CO3)2(OH)2), 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, often called King Solomon's Mines. 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.
Mozarkite
Mozarkite is a form of chert (flint). It is the state rock of Missouri. The name is a contraction of Mo (Missouri), zark (Ozarks), and ite (meaning rock).
Mozarkite consists essentially of silica (quartz - SiO2) with varying amounts of chalcedony. It has won distinction as a particular form or variety of chert because of its unique variation of colors and its ability to take a high polish. It has the hardness of 7-7.5 on the Mohs scale, which qualifies it as a suitable material for semi-precious gemstone, and has a density of about 2.65 g/cm3. Typically, the colors are different hues of red, pink, and purple with varying tints of green, gray and brown. It is collected and admired by lapidarists across the country.
Interest in collecting mozarkite in Missouri started in the early 1950s, in Benton County, Missouri. It is found primarily in west-central Missouri, south of the Missouri River, and west of the Lake of the Ozarks. Mozarkite occurs in the Cotter Dolomite of Ordovician age, which means it is some 450 million years old. It is found in residual boulders in the soil on hill slopes, along ditches, and in roadcuts where the boulders are exposed in the soil formed by weathering of the Cotter Dolomite.
Mozarkite was designated the official state rock of Missouri by the 74th Missouri General Assembly in 1967.
Turquoise
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).[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.[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.
Occurrence
Turquoise was among the first gems to be mined, and while many historic sites have been depleted, some are still worked to this day. These are all small-scale, often seasonal operations, owing to the limited scope and remoteness of the deposits. Most are worked by hand with little or no mechanization. However, turquoise is often recovered as a byproduct of large-scale copper mining operations, especially in the United States.
Agate
Agate (pronounced ['ægət]) is a microcrystalline variety of quartz (silica), chiefly chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks but can be common in certain metamorphic rocks.
Colorful agates and other chalcedonies were obtained over 3,000 years ago from the Achates River, now called Dirillo, in Sicily.
The stone was given its name by Theophrastus, a Greek philosopher and naturalist, who discovered the stone along the shore line of the river Achates sometime between the 4th and 3rd centuries BC.
Types of agate
A Mexican agate, showing only a single eye, has received the name of cyclops agate. Included matter of a green, golden, red, black or other color or combinations embedded in the chalcedony and disposed in filaments and other forms suggestive of vegetable growth, gives rise to dendritic or moss agate. Dendritic agates have fern like patterns in them formed due to the presence of manganese and iron oxides. Other types of included matter deposited during agate-building include sagenitic growths (radial mineral crystals) and chunks of entrapped detritus (such as sand, ash, or mud). Occasionally agate fills a void left by decomposed vegetative material such as a tree limb or root and is called limb cast agate due to its appearance.
Turritella agate is formed from silicified fossil Turritella shells. Turritella are spiral marine gastropods having elongated, spiral shells composed of many whorls. Similarly, coral, petrified wood and other organic remains or porous rocks can also become agatized. Agatized coral is often referred to as Petoskey stone or agate.
Greek agate is a name given to pale white to tan colored agate found in Sicily back to 400 B.C. The Greeks used it for making jewelry and beads. Today any agate of this color from Sicily, once an ancient Greek colony, is called Greek agate. Yet the stone had been around centuries before that and was known to both the Sumerians and the Egyptians, who used the gem for decoration and religious ceremony.
Another type of agate is Brazilian agate, which is found as sizable geodes of layered nodules. These occur in brownish tones interlayered with white and gray. Quartz forms within these nodules, creating a striking specimen when cut opposite the layered growth axis. It is often dyed in various colors for ornamental purposes.
Other forms of agate include carnelian agate (usually exhibiting reddish hues), Botswana agate, Ellensburg blue agate, blue lace agate, plume agates, tube agate (with visible flow channels), fortification agate (which exhibit little or no layered structure), fire agate (which seems to glow internally like an opal) and Mexican crazy-lace agate (which exhibits an often brightly colored, complex banded pattern) also called Rodeo Agate and Rosetta Stone depending on who owned the mine at the time.
Chrysacolla
Chrysacolla is a stone of harmony, both on a universal level and a very specific level. Chyrsocolla is a hydrous silicate of copper, occurring massive, of a blue or greenish blue color and is more appropriately a mineraloid than a true mineral. Chrysocolla is another one of Copper's crystal offspring.
It is available in green-blue color with a luster that is earthy to dull or vitreous and waxy. Pure chrysocolla is too soft for jewelry purposes but it is often found in quartz deposits which makes it hard enough to polish for cabochons.
Jasper
The name means "spotted or speckled stone", and is derived from Greek iaspis, (feminine noun)[3] via a Semitic language (cf. Hebrew yashepheh, Akkadian yashupu), ultimately from Persian yashp.
Green jasper was used to make bow drills in Mehrgarh between 4th-5th millennium BCE.[4] Jasper is known to have been a favourite gem in the ancient world; its name can be traced back in Hebrew, Assyrian, Persian, Greek and Latin. On Minoan Crete within present day Greece jasper was carved to produce seals circa 1800 BC based upon archaeological recoveries at the palace of Knossos.
The word yashepheh in the Masoretic text of Exodus 28:20, referring to a stone in the Hoshen, is thus reflected in the Septuagint by the word Iaspis, and usually translated into English as Jasper. Despite the most common form of Jasper being red, scholars think that the yashepheh here actually refers to a green form of Jasper - which was very rare, and so highly prized; the Greeks used Iaspis to refer to the green form, while the red form simply fell under the term Sard - which just means red. Rebbenu Bachya argues that this stone represents the tribe of Benjamin, but there is actually a wide range of views among traditional sources about which tribe the stone refers to.
It is described in the Book of Revelation (21:11) as follows: "It shone with the glory of God, and its brilliance was like that of a very precious jewel, like a jasper, clear as crystal."
Types of jasper
Jasper can appear as an opaque rock of shades of red due to mineral impurities. Patterns can arise from the formation process and from flow patterns in the sediment or volcanic ash that was saturated with silica to form jasper, yielding bands or swirls in the rock.
Jasper may be permeated by dendritic minerals providing the appearance of vegetative growths. The jasper may have been fractured and/or distorted after formation, later rebonding into discontinuous patterns or filling with another material. Heat or environmental factors may have created surface rinds (such as varnish) or interior stresses leading to fracturing.
A brown jasper that occurs as nodules in the Libyan desert and in the Nile valley is known as Egyptian jasper or Egyptian pebble.
Picture jaspers simultaneously exhibit several of these variations (such as banding, flow patterns, dendrites or color variations) resulting in what appear to be scenes or images in a cut section. Spherical flow patterns produce a distinctive orbicular appearance. Complex mixes of impurities produce color variations. Healed fractures produce brecciated jasper. Examples of this can be seen at Llanddwyn Island.
Orbicular jasper or leopard jasper is usually an opaque combination of tan, gray, black or reddish-brown circles or 'spots' of color, hence its name.
Bruneau jasper is a local variety from the region near the Bruneau River in western Idaho, United States. It exhibits deep maroon and gold colors that occur in orb-like patterns on the polished material.
Tiger Eye
Tiger's eye (also Tigers eye, 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. Tiger's eye is primarily composed of silicon dioxide (SiO2) and the specific gravity ranges from 2.64 -2.71 Formed by the alteration of crocidolite and consists essentially of quartz colored by iron oxide. Origin: South Africa and Australia
Notable sources of tiger's eye include the USA, South Africa, Canada, China, Brazil, Namibia, India and Burma.
Petrified Wood
Petrified wood (from the Greek root "petro" meaning "rock" or "stone", literally "wood turned into stone") is a type of fossil: it consists of fossil wood where all the organic materials have been replaced with minerals (most often a silicate, such as quartz), while retaining the original structure of the wood. The petrifaction process occurs underground, when wood becomes buried under sediment and is initially preserved due to a lack of oxygen. Mineral-rich water flowing through the sediment deposits minerals in the plant's cells and as the plant's lignin and cellulose decay away, a stone mould forms in its place. It probably takes less than 100 years for wood to petrify.
Elements such as manganese, iron and copper in the water/mud during the petrification process give petrified wood a variety of color ranges. Pure quartz crystals are colorless, but when contaminants are added to the process the crystals take on a yellow, red or other tint.
Following is a list of contaminating elements and related color hues:
· carbon - black
· cobalt - green/blue
· chromium - green/blue
· copper - green/blue
· iron oxides - red, brown, and yellow
· manganese - pink/orange
· manganese oxides - black/yellow
Petrified wood can preserve the original structure of the wood in all its detail, down to the microscopic level. Structures such as tree rings and the various tissues are often observed features.
Petrified wood has a Mohs hardness of 7, the same as quartz.
Petrified wood is the provincial stone of Alberta and also the state gem of Washington.
Turritella
Turritella is a genus of medium-sized sea snails with an operculum, marine gastropod mollusks in the family Turritellidae. They have tighly coiled shells, whose overall shape is basically that of an elongated cone.
The shells are quite frequently found as fossils, and the carbonate stone made from large quantities of Turritella shells is often referred to as "Turritella limestone", or, if silicified, "Turritella agate". Both varieties of this stone are commonly sold as polished cabochons.
The Turritellenplatte of Ermingen ("Erminger Turritellenplatte" near Ulm, Germany) is situated in the northern part of the North Alpine Foreland Basin (NAFB), and it is famous for its superabundance of Turritella turris gastropod shells within its sediments.
The genus is known from the Cretaceous to the recent periods.