Dolomitic lime is an attractive rock. It's calcium magnesium carbonate. It has about 50% calcium carbonate and 40% magnesium carbonate, giving approximately 22% calcium and at least 11% magnesium.hen you buy garden lime, it has been ground into granules that can be coarse or very fine, or it could be turned into a prill. Dolomite lime fertilizer is certainly allowed in organic gardening. It is not inherently bad, but how it is used in the garden is often detrimental.