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Description: Lithium sourcing feldspar
Oxide Analysis Formula Li2O 8.01% 1.00 Al2O3 27.41% 1.00 SiO2 64.59% 4.00 Oxide Weight 372.07 Formula Weight 372.07The 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.
Lithium carbonate is now ultra-expensive. Yet the reactive glaze on the left needs it. Spodumene has a high enough Li2O concentration to be a possible source here. It also has a complex chemistry, but the other oxides it contains are those common to glazes anyway. Using my account at insight-live.com, I did the calculations and got a pretty good match in the formulas (lower section in the green boxes). Then I made 10-gram balls and did a GLFL test at F (notice the long crystals in the glass pools below the runways). Not surprisingly, this recipe is very runny, that's why the tiny yellow crystals grow during cooling. The new version fires very similar, perhaps better. Our calculated cost to mix this recipe in was $17.84/kg vs. $10.40/kg. But there is a practical cost: Poor slurry properties. The spodumene sources so much Al2O3 that 70% Alberta Slip had to be dropped to accommodate it! How does one use this type of glaze without ruining kiln shelves? Using a catcher glaze is one answer.
Our theoretical chemistry is fairly close to this (notice these numbers are not precise, they indicate a range or minimum).
This is what happens when some spodumenes are mixed with water. They generate foam and bubbles. This is disruptive in glazes and can be alleviated by washing and drying the powder before use. Or calcining at 500-600F.
If you are looking for more details, kindly visit Dolomite Powder.
LA speckle test cone 10R (G spodumene) using ground ironstone concretions (50% 70-100 mesh, 35% 50-70 mesh, 15% 40-50 mesh) at 0.5%, 0.3%, 0.1% (left to right).
GA6-C (left) and GA6-E (right) at cone 6 oxidation. The E version adds 4% spodumene onto the 4% rutile in the C (the base is 80% Alberta Slip and 20% frit ). The spodumene eliminate the overly whitish areas that can appear. This glaze requires the "Slow Cool (Reactive Glazes)" firing schedule. It looks the best on dark bodies.
This is a closeup of GB, a recipe with 11% spodumene. Although the glaze is very glossy, its surface is marred by tiny dimples, the remnant of broken and partially healed bubbles escapes. These bubbles were in the laydown and dried in place (the spodumene generates these in the slurry itself, making it frothy). This can be reduced by drop-and-hold firing techniques, but a better answer is to find a frit to source the Li2O.
Spodumene ceramic grade, used in glazes, is a 200 mesh material. How could the particles be big enough to glisten in the light? This is a micrograph of some of the particles from the 0.6% plus 100 mesh material that I extracted in a particle size distribution test. And 8% is plus 200 mesh. And all that material is flakey like this, millions of tiny mirrors. This also explains why the material becomes airborne so easily and why it is really really not good to breathe this stuff in.
Of course, if a recipe only calls for 1-5% lithium carbonate either of these might be candidates to supply the Li2O. However, Petalite is eight times less and Spodumene five times less concentrated than lithium carbonate so to make either worthwhile the prices would need to be eight and five times cheaper. But if a recipe calls for more there is another problem: Petalite is extremely high in silica, which means supplying the needed Li2O from it is almost certainly going to oversupply SiO2. Spodumene will likely do the same. Both are also high in Al2O3 and likely to oversupply that (or at minimum supply the bulk preventing the presence of kaolin in the recipe).
Here's a fun fact for a Friday &#; Spodumene is a mineral that serves as an essential source of lithium. Did you know that its name comes from the Greek word &#;spodumenos,&#; meaning &#;burnt to ashes"? It was given this name due to the mineral&#;s tendency to become white or ash-coloured when exposed to air and high temperatures. There are so many interesting things to know about spodumene. To learn more, click on this link and read all about why the search for viable spodumene deposits continues. #mining #engineering #spodumene #lithium