Rockwool or stonewool is a very environmentally friendly product.  It is made by melting basalt rock and chalk, then spinning the molten rock into fibers, much like cotton candy.  These fibers are compressed and cut into the various sheets, cubes, blocks, etc.  One cubic foot of rock makes 37 cubic feet of rockwool.  The World Heath Organization has classified stonewool as a safe-to-use bio-soluble product.

Rockwool  Cubes are suitable for starting a wide range of plants, and is effective in growing anything from tomatoes, lettuce, flowers and even some aquatic plants. The cubes are attached at the bottom and the cubes are tapered toward the top.

The rockwool products are easily recycled.

1 Sheet = 25 Blocks