Ettringite

Ettringite is a rare calcium-aluminium sulphate and is one of the iconic minerals from the N'Chwaning Mines in the Kuruman Kalahari Manganese Field of South Africa.  This is a magnificent ex-matrix crystal forming a hexagonal prism with a six-sided pyramidal termination and central pinacoidal apex.  The Ettringite is a translucent, uniform brilliant acidic lemon-yellow, with a semi-transparent near-surface layer within which there is a fabulous satin lustre.  One side of the prism has grown against another crystal and hence has not had space to perfectly develop across three faces, forming a depressed phantom profile across these prism faces.  This is not damage, simply the Ettringite crystal accommodating the available development space.  A beautiful specimen and an exceedingly rare example of such perfect colour and display habit and, of course, its enormous size.