Calcite (twinned crystal)

Fabulous twinned Calcites from the West Cumbrian iron mines need little introduction as they are recognised the world over as true British classics.  This delightful specimen from Gillfoot mine, adjacent to the market town of Egremont in west Cumbria, is what is commonly termed a “heart-twin”, whereby the re-entrant angle sits at the apex, so making a heart-like shape.  These amazing specimens were relatively common in the late 1800 and early 1900s, but interestingly are not mentioned in Greg and Lettsom’s ‘Manual of the Mineralogy of Great Britain and Ireland’ published in 1858, so must have only been discovered post this publication.  This colourless gemmy calcite twin has mirror-smooth faces and typical deeply striated terminations, tinged slight pinkish-red by Hematite.  The crystals gave great transparency and grade into translucent zones with internal crazing.  A terrific and great example of this twinned habit.