Quartz

A spectacular bed of transparent colourless Quartz crystals covers a plate of massive milky Quartz of between 1 to 2 cm thick.  This magnificent specimen of museum quality and size is from Filon N°5, (Vein No. 5), one of several documented mineralised veins which traverse the wooded hillside at Les Rivoirands close to the commune of Vizille in south-eastern France.  The sharp crystals are typically 4 to 5 cm tall and almost all exhibit perfect Dauphiné habit terminations, whereby each termination has one greatly enlarged rhombohedral face. This habit is named after the Dauphiné, the old name for the French Alps around Grenoble from where this specimen is from.  Occasional crystals have normal habit, symmetrical hexagonal terminations.  The thickness of the crystals ranges between 0.5 and 1 cm, but occasional exceptional crystals occur of up to 2.2 cm wide.  The clarity can be described as gemmy and all have almost perfect optical transparency.  The prisms, and especially the terminations can adopt a pale lemon-yellow hue, typical of Quartz from Isère.  A magnificent Quartz specimen of Rock Crystal quality from Les Rivoirands, close to Grenoble.