Basalt Rock Dust
By releasing essential minerals and nutrients, rock deposits are essential to healthy plant growth and increased agricultural yields. However, not all rock amendment products are alike. For balancing overall soil health, basalt stands out from other rock materials. Created through the cooling and solidification of magma and lava, basalt is the rock material that makes up most of the soils around the world.
Compared to other volcanic rocks that are high in quartz, basalt weathers relatively quickly. It begins to release nutrients to plants as soon as the roots make contact. Additional nutrients become available with ongoing decomposition, thereby resulting in a steady flow of nutrients over time.
Basalt Rock Dust is made from igneous rock which means it hasn’t been processed or had any of nutrients leached, as a consequence it has most of the rare elements found in Azomite®, while having incredibly low levels of the elements that are more toxic (lead, arsenic, etc.).
Basalt has quite a high amount of silica and weathers much quicker than any other rock dust, so it becomes available quicker. It’s also a good slow source of phosphorus & potassium and will balance the pH of the soil. It provides some of the lowest sodium levels of any rock dust and is found in great amounts, so generally speaking, it is one of the cheapest rock dusts.
In my anecdotal experience, glacial rock dust and basalt together provide all the elements needed for mineralization of a medical garden.