Calcined Clay, Pumice & Expanded Shale
Calcined Clay is an essential soil amendment. Basically, it's like ground up brick. The calcined clay is fired at 1,200 or so degrees and becomes "rock" hard. Years from now it will be the same stuff in your potting medium as it was when you put it in there. Calcined Clay is used in lieu of sand because most of us cannot obtain the correct sizing of sands as most are usually too fine, being more like sugar or salt granules. Do not confuse this will cat litter which will break down into mush in contact with continuous moisture. Currently sold in 2, 4 and 8 quart bag sizes.
Microporous and light, pumice is ideal for improving aeration. It doesn't break down and the structures allows pockets of air to form. This white volcanic rock is ideal for bonsai soil mixtures. Pumice soil holds some water, but chiefly aerates the soil making it more porous. The variations you see in the colors here are because of the moisture one sample might have versus a dryer pumice which will be a lighter color. Currently sold in 2, 4 and 8 quart bag sizes.
Expanded Shale or Haydite is a product with basically everything you need for your Bonsai. It helps your Bonsai soil stay loose by increasing the porosity of the soil. Expanded shale for Bonsai soil conserves and holds water so you don't have to water as often even with our very porous soils and keeps you from the other extreme of over watering. It enhances root development and growth. This is mixed grain sizes, meaning small and medium grain sizes. Currently sold in 2, 4 and 8 quart bag sizes.