|If this formula is not unified correctly please contact us.|
|DENS - Density (Specific Gravity)||2.65|
|GSPT - Frit Softening Point||1710C M|
Unlike silica glass, the quartz phase of silica is subject to inversion and accompanying volume and form change when fired through 573C. Room temperature quartz is called alpha quartz, beta quartz exists only above 573C.
Quartz sand is often used in bodies as grog for texture and to increase thermal expansion. Powdered quartz is used in glazes and bodies also. Quartz of very fine particle size (-400 mesh) will typically enter the feldspathic melt or convert to cristobalite during firing if fluxes are lacking, coarse powdered grades help to 'squeeze' glazes into fit. Intermediate sizes (200-300 mesh) seem to be best however, since their greater surface area exerts more compressive squeeze per unit.
Crystalline silica is used in agriculture, paving, brick and tile, concrete, cleansers, foundry casting, ceramics and pottery, paint, glass, soaps, fiber glass, electronics, plaster, sandblasting, industrial effluent filtration, drinking water filtration, hazardous waste control.
Mineral, of the ideal form SiO2 with a typical empirical analysis of SiO2 100%
Hardness: 7 Density: 2.65 Soluble in HCl
There are two major groupings of quartz, and varieties are denominated according to color/opacity:
phanero-crystalline: crystals visible to the naked eye, such as:
rock crystal = clear; amethyst = violet; smoked = tan; pink = pink; morion or black = black; citrine = lemon yellow; blue = blue; tiger-eye = (can be cut to look like) a tigers eye; falcon-eye = (... like) a falcons eye; cat-eye = (...like) a cats eye; (the ... eye quartzes being pseudo-morphic); Aventurine = visible mica
and/or hematite inclusions; common = grey; milky = white; ferrous = visible iron deposits, etc.
crypto-crystalline: crystals visible through a microscope, such as chalcedony.
In contrast to the SiO2 of hydrous aluminum silicates, such as the feldspars and kaolins, the SiO2 of quartz is in its orderly (geometrically, uniformly, aligned morphic) more matured, crystalline form: practically speaking, it is more given to the infamous quartz-splitting than is a feldspar silica.
Splitting is less a concern with glaze coverings than with fabric bodies. When glaze crackling or crazing is desired, for example, quartzs inclination to split is a benefit. Subsequently, glaze recipes call for quartz much more frequently than do body fabric recipes. Fabrics (clay bodies) normally get their SiO2 from the silicas already comprising the clays being used (kaolin, feldspars, earthenware clays, etc.) and are calculated accordingly.
see refs to cristobalite, clay, feldspar, flint, glaze, silica, etc.
The piece on the left is 65% ball clay and 35% nepheline syenite. The one on the right is 65% kaolin and 35% nepheline syenite. Both fire vitreous at cone 6. But the glaze is crazing on the kaolin and not on the ball clay. This is because the ball clay contains significant quartz, that raises the thermal expansion and that puts the squeeze on the glaze and prevent the crazing.
Out Bound Links
Overview of quartz hazards in the ceramic industry and process
Quartz is the main crystalline mineral form of silica (SiO2). White or milky quartz is an opaque white, greasy-looking, sharply angular very hard rock. Natural deposits of relatively pure quartz are p...
In Bound Links
Quartz is one of the most dangerous materials used in ceramics, yet it is irreplaceable. It is the most abundant mineral on earth, we must learn to use it safely.
Silicon dioxide, silica, quartz sand
The hazards of this material in the ceramic industry and process
A checklist of for changes and additions to your tools and equipment and suggestions for habit changes you need to make to control dust
A measure of the reversible volume or length change of a ceramic material with temperature. The more the expansion during heating the more contraction must occur while cooling it back down. Expansion values are very small and recorded in scientific notation (e.g. 6.5 x 10-7 which is 0.00000065). Typ...
This term refers to an abrupt change in volume that occurs in quartz crystals when they are heated from the room temperature stable alpha phase to the...