The Siglo XX mine is one of the most impressive Bolivian mining localities. It produces some amazing specimens of common species like quartz, few of the with the Japan-Law twin which are are well known in the mineral world. In this sample we can enjoy a good sized Japan-twin quartz crystals, with transparence and luster. This nice twin is disposed on a druse of hyaline quartz crystals.
To give a unique touch to the specimen a group of cassiterite crystals with good brilliance and deep black color, very rich in faces, interpenetrating between them and with some quartz crystals. A superb specimen.