Glass

Once every 20 years the plate-glass factory in Tzipori relines its continuous [1700 degrees] kiln,dumping the last 500 ton melt of glass and selling off the high-alumina hard bricks to needy potters. Sydney,whose legendary brick reserve has dwindled to next to nothing,has bought some 20 tons of brick and some rather attractive lumps of glass,a couple of which I photographed. The white stuff is cristobalite,an alternative crystalline form of silica rarely occuring in nature,but somehow produced at the glass/brick interface by the extreme conditions in the kiln,and not to be confused with mullite ,another quartz morph,which is named after the Isle of Mull in Scotland.
We are planning to build a modestly-sized wood-fired kiln with a ton or so of the bricks,and are currently debating the virtues of Bourry-box versus fastfire [Olsen] designs, discussing heatedly the arcane art of kiln proportions and brushing up on our brick-laying technique. The 20 tons of brick are safely behind a wall where you can't see them,which is where Sydney tends to keep large piles of ceramic materials. We went to have a look at them this afternoon and we couldn't even see them.