The natural stones of Indonesia are obtained from solidified lava, and contain a mineral called zeolite. Its ionic properties purify the water, lowering the necessary amount of chlorine or salt, and the low porosity works as a barrier against bacteria on its surface and keeps the water temperature stable. It is a very non-slippery material and does not require special care.
It is possible – and attractive! – to mix the Sukabumi stones with Black Lava. You can alternate stones of the same size randomly, or surround the pool with a perimeter of Black Lava 15 × 15 and fill the interior with Sukabumi 10 × 10, for example.