Some minerals, such as phosphorous, do not move around well in the soil, while others, such as sulfur, can form a hardpan layer if not thoroughly mixed with the soil. Smaller-sized mineral particles will be more readily available to plants. This is especially true for rock minerals, such as greensand, that release nutrients very slowly. This rule doesn't apply to pelletized fertilizers, such as pelletized lime. Although these particles are larger than the crushed material, they are held together by a water soluble compound that quickly breaks down in the soil.
Pelletized fertilizers are less dusty and easier to use, but more expensive.
If you add rock mineral fertilizers to your soil, it is important to add organic matter as well. Organic matter helps stabilize the soil pH, which, in turn, increases microorganism activity. Microorganisms are key to breaking down the rock mineral fertilizers to usable form for the plant. Sulfur Apply in late spring or summer to lower pH of alkaline soils. Sulfur is mined in the western U.S., but most is a by-product of oil refining.