Type... Domestic Mineral This is a clay mineral found in clay veins (2-3 cm wide) growing on joint surfaces of weathered bedrock slopes observed in outcrops of biotite granite in the Tanakami granite area of Shiga Prefecture. The last two photos show the current state of the veins (the tan-colored streaks in the center) at the collection site. Clay was collected from these veins, dried, and is a very fine powder. The color is pale gray to white. It weighs about 80g. The content is expected to include sericite, which can be used as pottery clay, as well as montmorillonite, which expands when hydrated and is said to be a cause of slope failure, but is also effectively used as acid clay, and other various clay minerals. Therefore, this clay cannot be used for pottery. As this is a collection of natural clay as is, please understand that fine debris such as plant matter and organic matter may be mixed in (see photos). It will be shipped in a plastic bag via Mercari delivery.