Sphalerite with Quartz and Chalcopyrite

A great deal of crystallographic interest is packed into this quite charming miniature Sphalerite with Quartz and Chalcopyrite, from the Casapalca mine in Huarochiri Province, Peru.  The silver-black Sphalerite forms a roughly 3 x 3 x 3.5 cm multiple twinned crystal, the twinning manifested by linear grooves formed by deep re-entrant faces. Embedded in the Sphalerite are many epitaxially aligned Chalcopyrite crystals of typical brassy gold.  These vary in size and range from fairly intact crystals to those with many broken faces.  Some areas grade to translucent golden Sphalerite as the iron content rapidly reduces, with some patches so golden, they almost become indistinguishable from the Chalcopyrite.  The overall aesthetic is completed by an attached cluster of colourless to milky Quartz crystals.