Cassiterite from Aracual, Minas Gerais, Brazil

According to Mindat - Cassiterite is the primary ore of tin, which is found in hydrothermal veins and pegmatites associated with granite intrusions. Because of its durability it is also frequently found concentrated in alluvial placer deposits, sometimes in large enough quantities to be commercially exploitable, as in Malaysia, for example.

This specimen consists of a mass of highly lustrous, striated xls growing over what appears to be quartz.  A portion of the xl may have fractured, but I cannot say for sure.  Just pointing out what may be considered damage. Otherwise an attractive specimen to my eye.