Calcium sulphosilicate in lime-kiln wall coating

Green calcium sulphosilicate layers were formed in lime-larnite-calcite wall coating in a lime kiln at Rivervale, Western Australia. The compound formed in the kiln flame area by the combination of siliceous lime sand feed with sulphur trioxide from the sulphurous oil fuel. The calcium sulphosilicate is orthorhombic with a IOq83, b I5"4o8, c 6'825 A, space group Pcrnn. Crystals are [IoOl tablets or prisms elongated along c, D 2"95, hardness 5, streak pale green, decomposed by organic acids. Optical properties c~ I'632 = [ooI] blue, /3 I"638 = [200] yellow-green y 1-64o yellow-green, 2V~ = 60 ~ dispersion r > v, X-ray powder lines: 2"855 (IO) o32,2o2; 2"838 (7) 33o,32I ; 335 (6) o12; 2.622 (6) 33I ; 257t (6) 06o; 3"2o(5) 231 ; t"962 (5); I'899 (5); 1"896 (5); I'372 (5). Chemical analysis by P. Hewson gave: SiO2 21"5o, A1208 I'83, Fe~Oa 050, COs o'49, P205 o'23, CaO 57"I9, MgO o'35, Na~O o.22, K~O o.22, SrO o'I5, Li20 o.o6, SOa I6"7I, H20 + o.28, H20o.Io, others o'o4, total 99'87. On a water-free basis the unit cell contains Catg.6~ Mg0.17 Na• K0.0s Sr0.08 Lio.os 63+ p5$4.02 8i6.90 Alo.Ts Fe0.12 C0.~1 o.o6 O47.n, approximately 4[Ca,~(SiO4)2SO4], and isostructural with silicocarnotite, 4[Cas(PO4)2SiO4]. Type material is preserved at the Government Chemical Laboratories, Perth, Western Australia.