Cassiterite

An ex-matrix, spectacular twinned Cassiterite crystal from the mines at Horní Slavkov in the former Bohemia region of the Czech Republic.  The Cassiterite twin measures a huge 4.2 x 2.8 x 3.0 cm and is jet-black with glassy-smooth mirror-like faces and sharp, perfectly defined edges.  The re-entrant faces form a deep valley between the two crystals, with the outer faces displaying vertical furrows and striations.  There is a little bruising on some of the edges and one termination, but in all cases, this is minor and requires magnification to note such defects.  A conchoidal bruise has also been generated on one re-entrant face, although all such occurrences could be through natural damage while in-situ.  A choice and showy twinned Cassiterite from the Czech Republic.