The lava rock mined in Germany came to the earth's surface in liquid form at over 1000°C and cooled down there. It can be added to bonsai substrates as an aggregate in small grain sizes. The somewhat larger, handy stones are very suitable for root design (Seki-joju), as well as rock planting (Ishitsuki) or as decoration for landscape and forest design (Saikei/Yose-ue).
