KUNZITE[GEM]

Listing description

Kunzite is a pink to lilac colored gemstone, a variety of spodumene with the color coming from minor to trace amounts of manganese. Some (but not all) kunzite used for gemstones has been heated to enhance its color. It is also frequently irradiated to enhance the color. Many kunzites fade when exposed to sunlight.

Detailed description

Spodumene is a pyroxene mineral consisting of lithium aluminium inosilicate - LiAl(SiO₃)₂ - and is a source of lithium. It occurs as colorless to yellowish, purplish or lilac kunzite (see below), yellowish-green or emerald-green hiddenite, prismatic crystals, often of great size. Single crystals of 14.3 m (47 ft) in size are reported from the Black Hills of South Dakota, United States.^[5]

The normal low temperature form α-spodumene in the monoclinic system whereas the high temperature β-spodumene crystallize in the tetragonal system. The normal α-spodumene converts to β-spodumene at temperatures above 900 °C.^[4] Crystals are typically heavily striated parallel to the principal axis. Crystal faces are often etched and pitted with triangular markings.

Discovery and occurrence

Spodumen was first described in 1800 for an occurrence (the type locality in Utö, Södermanland, Sweden. The name is derived from the Greek spodumenos (σποδυμενος), meaning "burnt to ashes," owing to the opaque, ash-grey appearance of material refined for use in industry.^[1]

Spodumene occurs in lithium rich granite pegmatites and aplites. Associated minerals include: quartz, albite, petalite, eucryptite, lepidolite and beryl.^[2]

Transparent material has long been used as a gemstone with varieties kunzite and hiddenite noted for their strong pleochroism. Source localities include Afghanistan, Australia, Brazil, Madagascar, Pakistan, Québec in Canada and North Carolina, California in the USA.

Economic importance

Spodumene is an important source of lithium for use in ceramics, mobile phone and automotive batteries, medicine and as a fluxing agent. Lithium is extracted from spodumene by fusing in acid.

World production of lithium via spodumene is around 80,000 metric tonnes per annum, primarily from the Greenbushes pegmatite of Western Australia, and some Chinese and Chilean sources. The Talison mine in Greenbushes, Western Australia has an estimated reserve of 13 million tonnes.^[6]

Some think that spodumene will become a less important source of lithium due to the emergence of alkaline brine lake sources in Chile, China and Argentina, which produce lithium chloride directly. Lithium chloride is converted to lithium carbonate and lithium hydroxide by reaction with sodium carbonate and calcium hydroxide respectively.

But, pegmatite based projects benefit from being quicker to move into production than brines - which can take 18 months to 3 years depending on evaporation rates. With pegmatites, once a mill is built, the production of lithium carbonate is only a matter of days.

Another key edge that spodumene has over its more popular brine rivals, is the purity of the lithium carbonate it can produce. While all product used by the battery industry have to grade at least 99.5% lithium carbonate, the make up of that final 0.5% is important. If it contains higher amounts of iron, magnesium or other deleterious materials it is less attractive to end users.

Gemstone varieties

Hiddenite

Hiddenite is a pale emerald green gem variety first reported from Alexander County, North Carolina, U. S. A.

Kunzite

Kunzite is a pink to lilac colored gemstone, a variety of spodumene with the color coming from minor to trace amounts of manganese. Some (but not all) kunzite used for gemstones has been heated to enhance its color. It is also frequently irradiated to enhance the color. Many kunzites fade when exposed to sunlight. It was discovered in 1902, and was named after George Frederick Kunz, Tiffany & Co's chief jeweler at the time, and a noted mineralogist. It has been found in Brazil, USA, Canada, CIS, Mexico, Sweden, Western Australia, Afghanistan and Pakistan.

Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable. For this reason, it is typically stored in mineral oil. When cut open, lithium exhibits a metallic luster, but contact with moist air corrodes the surface quickly to a dull silvery gray, then black, tarnish. Because of its high reactivity, lithium never occurs free in nature, and instead, only appears in compounds, usually ionic ones. Lithium occurs in a number of pegmatitic minerals, but is also commonly obtained from brines and clays. On a commercial scale, lithium is isolated electrolytically from a mixture of lithium chloride and potassium chloride.

The nuclei of lithium are not far from being unstable, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. As a result, they can be used in fission reactions as well as fusion reactions of nuclear devices. Due to its near instability, lithium is less common in the solar system than 25 of the first 32 chemical elements even though the nuclei are very light in atomic weight.^[1] For related reasons, lithium has important links to nuclear physics. The transmutation of lithium atoms to tritium was the first man-made form of a nuclear fusion reaction, and lithium deuteride serves as a fusion fuel in staged thermonuclear weapons.

Atomic and physical

Like the other alkali metals, lithium has a single valence electron that is easily given up to form a cation.^[2] Because of this, it is a good conductor of heat and electricity as well as a highly reactive element, though the least reactive of the even-more highly reactive alkali metals. Lithium's low reactivity compared to other alkali metals is thought to be due to the proximity of its valence electron to its nucleus (the remaining two electrons in lithium's 1s orbital and are much lower in energy, and therefore they do not participate in chemical bonds).^[2]

Lithium metal is soft enough to be cut with a knife. When cut, it possesses a silvery-white color that quickly changes to gray due to oxidation.^[2] While it has one of the lowest melting points among all metals (180 °C), it has the highest melting point of the alkali metals.^[3]

It is the lightest metal in the periodic table. It has a very low density, of approximately 0.534 g/cm³, which gives sticks of the metal a similar heft to dowels of a medium density wood, such as pine. It floats on water but also reacts with it.^[2] It is the least dense of all elements that are not gasses at room temperature. The next lightest element is over 60% more dense (potassium, at 0.862 g/cm³). Furthermore, aside from helium and hydrogen, it is the least dense element in a solid or liquid state, being only 2/3 as dense as liquid nitrogen (0.808 g/cm³).^{[note 1][4]}

Chemistry and compounds

Lithium reacts with water easily, but with noticeably less energy than other alkali metals do. The reaction forms hydrogen gas and lithium hydroxide in aqueous solution.^[2] Because of its reactivity with water, lithium is usually stored under cover of a viscous hydrocarbon, often petroleum jelly. Though the heavier alkali metals can be stored in less dense substances, such as mineral oil, lithium is not dense enough to be fully submerged in these liquids.^[9] In moist air, lithium rapidly tarnishes to form a black coating of lithium hydroxide (LiOH and LiOH·H₂O), lithium nitride (Li₃N) and lithium carbonate (Li₂CO₃, the result of a secondary reaction between LiOH and CO₂).^[10]

When placed over a flame, lithium compounds give off a striking crimson color, but when it burns strongly the flame becomes a brilliant silver. Lithium will ignite and burn in oxygen when exposed to water or water vapors.^[11] Lithium is flammable, and it is potentially explosive when exposed to air and especially to water, though less so than the other alkali metals. The lithium-water reaction at normal temperatures is brisk but not violent, though the hydrogen produced can ignite. As with all alkali metals, lithium fires are difficult to extinguish, requiring dry powder fire extinguishers, specifically Class D type (see Types of extinguishing agents). Lithium is the only metal which reacts with nitrogen under normal conditions.^[12][13]

Occurrence

Astronomical

According to modern cosmological theory, lithium—as both of its stable isotopes lithium-6 and lithium-7—was among the 3 elements synthesized in the Big Bang. Though the amount of lithium generated in Big Bang nucleosynthesis is dependent upon the number of photons per baryon, for accepted values the lithium abundance can be calculated, and there is a "cosmological lithium discrepancy" in the Universe: older stars seem to have less lithium than they should, and some younger stars have far more. The lack of lithium in older stars is apparently caused by the "mixing" of lithium into the interior of stars, where it is destroyed.^[26] Furthermore, lithium is produced in younger stars. Though it transmutes into two atoms of helium due to collision with a proton at temperatures above 2.4 million degrees Celsius (most stars easily attain this temperature in their interiors), lithium is more abundant than predicted in later-generation stars, for causes not yet completely understood.

Terrestrial

Although lithium is widely distributed on Earth, it does not naturally occur in elemental form due to its high reactivity.^[2] The total lithium content of seawater is very large and is estimated as 230 billion tonnes, where the element exists at a relatively constant concentration of 0.14 to 0.25 parts per million (ppm),^[31][32] or 25 micromolar;^[33] higher concentrations approaching 7 ppm are found near hydrothermal vents.^[32]

Estimates for crustal content range from 20 to 70 ppm by weight.^[10] In keeping with its name, lithium forms a minor part of igneous rocks, with the largest concentrations in granites. Granitic pegmatites also provide the greatest abundance of lithium-containing minerals, with spodumene and petalite being the most commercially viable sources.^[10] A newer source for lithium is hectorite clay, the only active development of which is through the Western Lithium Corporation in the United States.^[34] At 20 mg lithium per kg of Earth's crust,^[35] lithium is the 25th most abundant element. Nickel and lead have about the same abundance.

PRICE

$378554.27/KG OR $172070.12/IB

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