Spodumene (Sold in .25Units)

The name is from the Greek spodos, meaning burnt to ash. Spodumene is a silicate mineral often referred to as lithium feldspar. Its mineral form is characterized by hard needle-like grains of brilliant white color. It is used in ceramics as a source of lithia.

In ceramics, lithia is a very powerful flux, especially when used in conjunction with potash and soda feldspars. As one of only a few natural lithium source materials, spodumene is a valuable component in glass and ceramic/enamel glazes (Li₂O reduces thermal expansion, melting temperature and viscosity of the glaze melt). It was also used in huge quantities to make Corning Ware.

Spodumene is only slightly soluble (in contrast to lithium carbonate). Because spodumene is a natural combination of silica, alumina and lithia it melts better than a chemically equivalent mixture of lithium carbonate, kaolin and silica. Since almost all raw glazes contain kaolin and silica it is normally fairly easy to juggle recipe ingredients, using glaze chemistry, to replace lithium carbonate with spodumene (provided, of course, that the lithium carbonate percentage is not too high). Spodumene can also be substituted for part of the feldspar complement in a recipe without disturbing overall chemistry too much (other than substituting Li₂O for KNaO).

That being said, the price of spodumene is increasing rapidly as industry learns to extract the lithium from it. This is being done via calcination to convert the crystal structure from monoclinic alpha (a-form) to tetragonal beta (β-form). Calcination is then further employed in the acid roasting of spodumene, so that lithium can be extracted as water-soluble lithium sulfate.

Some types of spodumene do contribute to the formation of bubbles in the glaze slurry. You can wash spodumene before use to alleviate this issue (mix it well in plenty of hot water, allow to settle overnight, pour off the water the next day and dry it).

Spodumene is a little more readily fusible than petalite since it is higher in lithium. It is considered a better source of Li₂O for frits. Some sources quote the percentage of Li₂O in molar percent rather than weight percent (resulting in a much higher figure).

Spodumene powder, although heavy, dusts easily and is very unpleasant to smell or breathe. And it sticks to tools, scoops and containers. Good ventilation equipment is essential when working with it.