Lava rock is commonly used in bonsai soil mix to prevent compaction. The smaller lava rock is a traditional ingredient added to Bonsai soil mixes. Lava rock will not break down over time. It is non toxic and completely reusable which makes it an ideal component for soil mixes. The porous structure of the lava rock also allows for water retention. Ideal for junipers and pines.

Mt. Fuji Black Lava Rock is specially sourced from Mt. Fuji in Japan for use in bonsai soil. 

Lava Rock (Black) Small Grain information:

• Ingredients: Black Bonsai Grade Lava Rock
• Excellent for preventing compaction
• Provides drainage, aeration, and water retention