Willemite Mineral Data, see http://www.webmineral.com/data/Willemite.shtml

Willemite from Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Willemite

Willemite from Alkali Nuts http://www.saint-hilaire.ca/en/willemit.htm

Willemite crystal © Gilles Haineault

The following are excerpts from 5Microscopy and microanalysis of crystalline glazes, K. M. KNOWLES & F. S. H. B. FREEMAN, University of Cambridge, Department of Materials Science & Metallurgy, Pembroke Street, Cambridge, CB2 3QZ, U.K.

 Crystalline glazes…have been examined…to identify the crystalline phases present…

X-ray diffraction of these crystals identified these crystals as willemite, a-Zn₂SiO₄. 

Crystals are…macroscopic two-dimensional spherulites within the glazes clearly seen by the naked eye were found to consist of large numbers of radially orientated acicular crystals each 5 mm (micron) or less in width embedded within the silica-rich glaze. ….almost always referred to incorrectly in such literature as ‘crystals’ or as ‘individual crystals’ rather than as spherulites.

 Direct measurement of the width of the individual acicular needles seen most easily in Fig. 5(d) suggests that their width is typically 2–3 mm and at most 5 mm.

5 micron ~ .0002 in. ~ 1/25^th the diameter of a human hair

 the 100–150 mm thick surface glaze

Spherulite                A spherical body, or coarsely crystalline aggregate having a radial internal structure arranged about one or more centers (McGraw-Hill Dictionary of Scientific and Technical Terms)

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Phil Hamling

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