Cover image: root replacement pipe crystal boulder opal from Australia. 11.8 × 6.0 x 3.8 mm and 1.62 carats (credit: Tom Goskar). My mind regularly imagines its way through the microscopic worlds of gems, minerals and rocks we can’t see. The jumping atoms causing interesting colours, the crystal lattices literally bending light in different directions,… Continue reading Behind the opal rainbows of October