Spodumene is a mineral with a hardness of 7 out of 10 on the Mohs scale of mineral hardness [?]. These Monoclinicly structured gems are made of lithium aluminum silicate, their full chemical compound being LiAl(SiO3)2.
Spodumene is a lithium aluminum silicate that crystallizes in the monoclinic system. It is one of several rock-forming minerals in the Pyroxene group, which are physically-related as their chemical content is quite similar and forms a chain. Fellow pyroxenes are jadeite, enstatite, diopside, hypersthene, augite, acmite, hedenbergite, pigeonite, and aegirineaugite.
It appears as prismatic crystals, sometimes gigantic. One sample was 16m/53ft long and weighing several tons, with vertical striations. It also forms rodlike aggregates of cryptocrystalline masses, like gelatinous masses that slowly solidified. Crystals can be whitish, yellow, gray, pink (kunzite), or emerald-green (hiddenite). It is a trichroic mineral, changing color depending on the angle at which it is viewed.
It is hard, heavy, has perfect cleavage parallel to the vertical prism. It is transparent to translucent, with vitreous luster. It is insoluble, fuses easily, coloring the flame crimson (lithium).
Spodumene occurs in lithium-bearing pegmatites associated with quartz, feldspars, lepidolite, beryl and tourmaline. It is often subject to layer alteration, turning mixtures of various minerals, including clays, albite, muscovite, eucryptite, etc.
Spodumene is mined intensively at Etta and Tin Mountain, in the area of the Black Hills of South Dakota (USA), where enormous crystals are found; in Bernic Lake, Manitoba (Canada), and in the Urals (Russia). It occurs in many places in the USA, Brazil, Mexico, Scotland and Sweden. Kunzite is found at Pala, California (USA), and in Brazil, and hiddenite in North Carolina (USA), and Madagascar.
The known varieties of gem-quality spodumene are:
The violet pink, transparent variety of spodumene, named after the American mineralogist George Frederick Kunz, a noted mineral collector and gem expert active at the turn of the century. The characteristic color is a violet pink, which can be quite intense. It can look very much like pink topaz and morganite, but kunzite has the strongest pleochroism among the three, best seen in larger, richer-colored stones.
The green variety of spodumene, which has only been known for about a century, and is named after William Earl Hidden, a mine-owner in the United States, who was actually looking for platinum where the mineral was first discovered (in North Carolina). Some people nowadays say that the name hiddenite refers only to emerald green spodumene, but others apply the name to all gem-quality green spodumene. You would be right to imagine that after so many years of mining, hiddenite has become a rare gemstone.
Some commercial terms used for spodumene are:
Californian iris - a misleading and fanciful term for kunzite, a variety of spodumene, from California, USA.
Cat's-eye kunzite - a pink to violet variety of spodumene that exhibits chatoyancy, when cut en cabochon.
Cat's-eye spodumene; a white variety of spodumene, from Brazil, that exhibits chatoyancy.
Misleading terms include:
Emerald spodumene - a misleading term for hiddenite.
Spodumene basically means "ashen," because the non-transparent material of this mineral which is for industrial use is often grayish white or ash gray. In the past it was also called "triphane," a Greek-derived word meaning "three aspects," due to its clear trichroism.
Spodumene is an important industrial source of lithium and its salts. Formerly needed mostly for nuclear weapons production and glass manufacturing, lithium is now experiencing considerable resurgence in demand because of our need for lithium-ion batteries.
Violet pink, bright green, yellow green or yellow gem-quality specimens of spodumene are much less common, and transparent crystals of these are used as gems. The semiopaque crystals look almost pearly.
Kunzite spodumene crystals used as gems generally have few inclusions and good transparency. Its perfect cleavage makes this gem quite brittle, sensitive to knocks, and therefore not ideal as a ring stone. It is usually given a (sometimes quite elongated) oval mixed cut, a pear-shaped or triangular mixed cut, or even a step cut. Its value is not very high. As secondary gems go, it is more or less on the same level with good quality red garnets. Pale pink corundum is often used to imitate kunzite.
The best, and now fairly rare specimens of Hiddenite spodumene are a bright green, almost like that of emerald, and have a transfixing columnar splendor in its natural state. But most hiddenite may appear as dull, pale green, or even green with a yellowish tinge. The step cut is used for it. Strongly-colored stones are usually small to medium-sized, but never as large as kunzite. Its attractive color, rarity, and the difficulty of finding reasonable-sized stones make hiddenite gems of intense color one of the most valuable secondary gems. But paler-colored specimens are valued lower, like kunzite.