Aragonite/Oyster Shell Flour

Aragonite/Oyster Shell Flour is a natural coral-sea calcium amendment (0-0-0-94 Ca) that is high in calcium and low in magnesium. This pure calcium source nourishes soil microbes and raises biological activity, serving as a natural alternative to lime for living organic soils, gardens, compost, and raised beds.

At a glance

• Type: Natural calcium soil amendment (aragonite/oyster shell flour)
• Analysis: 0-0-0-94 Ca
• Calcium content: 97% calcium carbonate and calcium silicate combined; 33% minimum to 40% available calcium
• Trace minerals: Fe2O3 0.025%, Al2O3 0.15%, MgCO3 1.50%, SO3 0.20%, NaCl 1.25%, SrO 1.25%, SiO2 0.88%
• Certification: Organic
• Application rate: 1 to 2 cups per cubic foot of soil
• Shipping: Free shipping on the 45 lb option

Best for

• Living organic soils that benefit from a low-magnesium calcium source
• Gardens, containers, and raised beds
• Building mineral balance alongside a broader nutrient regimen
• A natural alternative to lime
• Use as a top layer for bocce courts

How to use

Use 1 to 2 cups per cubic foot of soil to complement your broader nutrient and mineral regimen. Mix into garden soil, containers, raised beds, or compost to supply calcium and nourish soil microbes.

About The Soil Makers

The Soil Makers craft mineral and biology-friendly inputs designed to boost nutrient availability and mineral balance across gardens, compost, and raised beds.