Red lava rock is a main orchid media mix especially in Hawaii. Lava rock is an excellent base for an inorganic rock mix. This lava rock has good water retention with excellent aeration. Because it is inorganic, the mix will not break down and orchids that resent repotting can be left in their mix longer. .
Perfect for growing media mix of paphiopedilum orchids, You can learn more at http://staugorchidsociety.org/PDF/201002Tips-GrowingPaphsinLavaRock.pdf