Calcite with Stilbite

Calcite with Stilbite from the iron mines around the city of Rudny in Kostanay Province, Kazakhstan.  Wow, what a beautiful specimen!  This is one of those specimens which sounds simple (which it is) and nothing out of the ordinary, but when you see it, extracts a fair few exclamations of “Wow!”.  Small yet perfect Roman sword Stilbite crystals cover the top surface of a creamy granular matrix and on top of these sit five pairs of perfectly formed twinned Calcite crystals.  The pairs range from 2 to 5 cm wide and all are semi-transparent to translucent, smoky opalescent light grey with a pearly lustre.  I must emphasise opalescent because the Calcite is a superb example of this optical property, displaying a slightly blue cast similar to moonstone; the colloquial name for pearly and opalescent microcline and orthoclase feldspar.  As mentioned, all crystals are twinned, with each perfectly displaying crisp re-entrant angles.  I can see no damage at all on the specimen.  It’s a beautiful and highly displayable example of Calcite with Stilbite from Rudny.