This is an awesome specimen of Herkimer "Diamond" Quartz from Herkimer, New York. Herkimer "Diamonds" are not actual diamonds. They are a type of quartz. It Every Herkimer Quartz is double terminated, which is how it got it's "Diamond" nickname. This specimen has two large crystals growing together. The stones are mostly clear all the way through. They have black carbon inclusions on the back that get magnified by the internal shape of the quartz and reflected on the walls. It looks really cool when you turn it to see these appear and disappear in the different faces. One of the crystals also has some skeletal structures on several faces.
This piece measures approximately 6cm x 5.2cm x 3.4cm