What is Spodumene?
Spodumene is a pyroxene mineral that is found, almost exclusively, in granite pegmatites. It has a chemical composition of
LiAlSi2O6 but small amounts of sodium sometimes substitute for lithium.
Spodumene is typically found in lithium-rich pegmatites in association with other lithium minerals such as lepidolite, eucryptite and petalite.
In the historical literature the mineral is often referred to as "triphane."
Enormous Crystals
Spodumene often occurs in extremely large crystals. One of the earliest accounts of large spodumene crystals is from the
Etta Mines, Black Hills, Pennington County, South Dakota. The United States Geological Survey, Bulletin 610 reports:
"The crystals are often of enormous size. In the Etta Mine, where they are best exposed both in the open cut and tunnel, they
frequently attain a diameter of 3 to 4 feet and a length of 30 feet. The largest "log" so far found was 42 feet long and
5 feet 4 inches in maximum diameter. This one log alone would yield 90 tons of spodumene." [1]
| Molds of giant spodumene crystals at the Etta Mines, Black Hills, Pennington County, South Dakota. Note miner at right center for scale. USGS photo. [1] |
Uses of Spodumene
Spodumene once served as the most important ore of lithium metal. Although it remains an important source of lithium, today most of the world's
lithium is produced from subsurface brines in Chile, Argentina, and China. These sources of lithium have lower production costs and are suitable
for most uses. However, when lithium of highest
purity is needed, spodumene is the source that is used.
Physical Properties of Spodumene |
| Color |
White, gray, yellow, green, blue, lilac, pink, brown. Sometimes pleochroic. |
| Streak |
White, colorless. |
| Luster |
Vitreous, pearly. |
| Diaphaneity |
Transparent to translucent. |
| Cleavage |
Perfect in two directions with parting. |
| Mohs Hardness |
6.5 to 7 |
| Specific Gravity |
3.1 to 3.3 |
| Distinguishing Characteristics |
Prismatic crystals with strong striations parallel to their principal axis. Perfect cleavage. |
| Chemical Composition |
LiAlSi2O6 |
| Crystal System |
Monoclinic (low temperature) tetragonal (high temperature). |
Spodumene as a Gemstone
Spodumene sometimes occurs in transparent crystals in pastel shades of pink, green and yellow. These
have been cut into gemstones that are prized by collectors. However, their use in jewelry is limited
to pieces that will be subject to limited abuse because of spodumene's perfect cleavage.
Kunzite
Pink to lilac specimens of gem-quality spodumene are highly prized and known as "kunzite".
The color of these specimens is attributed to the presence of manganese as a chromophore. Kunzite is
the most commonly encountered spodumene gem.
Many specimens of kunzite are strongly pleochroic with the deepest color observed when the gem is
viewed down the principal axis. To take full advantage of its phenomenon, gemstones are cut with
the table perpendicular to the principal axis to yield stones of the deepest color.
Some kunzite will develop a richer color when heated or irradiated. These procedures have been
applied to some stones that enter the marketplace. Some specimens of kunzite will fade over time when
exposed to direct sunlight. Valuable stones should be stored away from direct light and, to be conservative, in a closed container.
Hiddenite
Emerald green spodumene is known as "Hiddenite." Its vivid green color is very similar to emerald
and is attributed to the presence of chromium as a chromophore. It is the rarest gem variety of spodumene.
It was first found near the town of Stony Point, North Carolina, which changed its name to "Hiddenite" after
the popular gemstone that attracted people to the area.
Other Colors
Yellow and clear specimens of spodumene have also been cut into gems; however, variety names for spodumene
gems have only been given to Kunzite and Hiddenite.
Demand for Spodumene
The demand for spodumene is dependent upon the use of lithium in manufacturing. In the past, most lithium
compounds and minerals were used to produce ceramics, glass, aluminum alloys and high-temperature grease.
However, an exploding demand for rechargeable batteries to power cell phones, tablet computers, cameras, music players, GPS units and other portable
electronic devices is driving the demand for high-purity lithium - and that drives the demand for spodumene.
Lithium batteries have a much
higher charge-to-weight ratio and power-to-weight ratio than lead/acid and zinc carbon cells.
This makes lithium the battery material of choice.
Lithium produced from spodumene has fewer contaminants than lithium produced from brines. These contaminants can interfere with battery performance and make spodumene the preferred choice for battery lithium. A new battery technology could displace the use of lithium; however, most new battery
technologies have been lithium-based.
Contributor: Hobart King
More from Geology.com
| Sunstone: A feldspar with aventurescence caused by light reflecting from platy inclusions. |
| Rocks: Photos of igneous, sedimentary and metamorphic rocks. |
|
|
| Minerals: The building blocks of our society. We use items made with minerals every day. |
| Volcanoes: Articles about volcanoes, volcanic hazards and eruptions past and present. |
|
|
 |
| Translucent to transparent spodumene with an attractive pink, yellow or green color is sometimes faceted, cut en cabochon or used to make tumbled stones. Its perfect cleavage
limits its use to jewelry that will not be subject to rough wear or handling. Spodumene is primarily a "collector's gemstone." The larger pieces of spodumene in this image are about one inch long. |
| Pink gem-quality spodumene (kunzite) from the Konar Valley, Konar, Afghanistan. Creative commons image by Didier Descouens. |
| An ore-grade spodumene crystal section showing cleavage and typical striations. Photograph by Andrew Silver, USGS, BYU Collection. |
| Lithium has many diverse uses. This chart shows estimated global uses of lithium by end product.
It is mainly used in manufacturing ceramics, specialty glass, rechargeable batteries, high-temperature grease,
continuous castings, polymers, aluminum alloys and pharmaceuticals. USGS data. [2] |
| One of the primary uses of spodumene is in the production of high-purity lithium for use in
lithium-ion batteries. The popularity of small electronic devices such as cell phones, portable computers and cameras is driving the demand for spodumene. Photo © Anton Snarikov, iStockphoto. |
 |
Did You Know?
Lithium is an active ingredient in some medications. Salts of lithium are used in medication for bipolar disorder. The lithium contributes to a "mood-stabilizing" effect.
One product has been named "Lithium." Image © Paige Foster, iStockphoto. |
[1] Mineralogic Notes, Series 3:
Waldemar Schaller, Gigantic Crystals of Spodumene, United States Geological Survey, Bulletin 610, 1916.
[2] Lithium: Brian Jaskula, United States Geological
Survey, Mineral Commodity Summary, January 2012.
[3] Lithium: Brian Jaskula, United States Geological Survey,
Minerals Yearbook, December, 2011.
|
|
