Vermiculite is made from compressed dry flakes of a silicate material which is absorptive and spongy. The color of vermiculite is a golden brown to a dark brown and is a sometimes difficult to tell from the potting soil it’s mixed with.
Vermiculite helps to aerate soil while simultaneously retaining water and nutrients, which it then releases over time. Vermiculite is therefore useful in seed sowing and propagation. It can also be added to house plant compost.