Evening Meeting and AGM - Talk by Bill Bagley - "The Wonders of Calcite"
Eighteen members attended the first meeting of the year despite the wind and rain. The AGM was followed by a very interesting talk by Bill Bagley in which he gave an overview of the mineral calcite. Bill took us through the processes of formation including a short video clip of the rare type of volcano producing carbonatite i.e. Doinyo Lengai volcano in Tanzania. With photos he explained calcite's structure and colour variations. That the most common crystal forms are scalenohedra, and rhombohedra and calcite readily cleaves into rhombohedra. It may also occur as prismatic crystals. The crystals may be tabular, acicular, prismatic and platy. Calcite can occur as crystals, stalactitic, massive, earthy, as aggregates or in geodes. The colour of calcite can vary from colourless through white, yellow, brown, reddish, bluish to black. It is also one type of mineral that shows birefringence.
The talk, along with the numerous impressive specimens that Bill brought from his own collection made for a very interesting evening.