The element sulphur was ubiquitous in all of the pigments and occurred at higher levels in the whewellite samples in the form of gypsum.
Our report of the widespread presence of oxalates as pigments was the first record of oxalates as pigments in their own right, or of them being the major alteration of other pigments to whewellite (Ford, MacLeod & Haydock, 1994).
In biochars produced at 550[degrees]C from eucalyptus materials (samples 2, 4, 6 and 13), no distinctive peaks of whewellite were found in their XRD spectra (Singh et al.
1 Whewellite Ca, K, Mg 2 Calcite Ca, K, Mg 3 Whewellite Ca, K, Mg 4 Calcite Ca, K, Mg 5 Whewellite Ca, K, Mg, Na 6 Calcite, sylvite Ca, K, Mg, Na 7 Calcite, kaolinite Ca, Mg 8 Sylvite, quartz, calcite Ca, K, Mg, Na 9 Sylvite, quartz, calcite Ca, K, Mg, Na 10 Sylvite, quartz, calcite, kaolinite, albite Ca, K, Mg, Na 11 Sylvite, quartz, calcite, kaolinite, albite Ca, K, Mg, Na 12 n.
3 C,D (rhomboid-shaped  pinacoids) is characteristic of whewellite (Hartl et al.
The performed spectroscopic studies supported by some X-ray powder diffraction measurements as well as by the obtained scanning electron microscopy images, definitively confirm the presence of calcium oxalate in the form of whewellite, in all the investigated samples.
Most of these are very good and some are outstanding, especially the big Cornwall bournonite, the miniature of green muscovite from North Carolina, the matrix analcime from the Phoenix mine, Michigan, and a German pyrolusite and German whewellite