Amethyst with Cristobalite
The Cristobalite is one of the three silica forms, it crystallized at an higher temperature compare to quartz: 1710C° instead for the quartz is 870 C° and the tridimite is 1470C°.
Generally the crystals are fibrous-rounded balls and in this amethyst are very visible.
Unusual stone for collector.
Size: 19.4x15.4x5.7 mm.
Weight: 15.21 ct.