Orthoclase with Albite, Schorl

Orthoclase with Albite and Schorl from Lake Boga Quarry, Lake Boga, Victoria, Australia, measuring 65 × 45 × 40 mm and weighing 132 grams.

Orthoclase and Albite are both feldspars, the two most abundant minerals in granite and the pegmatites that crystallise from it, and finding them together with Schorl, the common black iron-rich member of the tourmaline group, is a classic late-stage pegmatite assemblage. Schorl typically crystallises from the final, most chemically evolved fluids left in a cooling pegmatite, often after the bulk of the feldspar has already formed, so its presence alongside the two feldspars here tells a small story about how this pocket finished crystallising.

This piece comes from the Allan Waldon Collection. Lake Boga, in Victoria's north, is a useful locality for anyone wanting to see classic granite pegmatite mineralogy from an Australian source rather than the more commonly offered overseas material.