Chemically, aragonite is identical to the more common calcium carbonate polymorph, calcite. The differences between the two materials are the result of their different crystalline structures, as a result the characteristics of Bahamian aragonite are compared to calcite (terrestrial limestone) in most markets.
Unique properties such as the orthorhombic structure of the oolitic aragonite crystal and a strong negative zeta potential add to the materials ability to out-perform calcite. This has most recently been observed in the GCC markets in which these polymorphs (calcite and aragonite) of CaCO3 directly compete. Historically calcite has been used as a mineral filler because it is a plentiful and relatively cheap filler. Beginning in 2012, testing in plastic and polymer applications began to show added product strength in formulas using aragonite directly compared with those using calcite. Product runs generated stiffer and more durable plastic food trays and polymer products like molding and decking. These results are a clear indication of performance benefits not previously seen with calcite, and are directly attributed to aragonite’s crystalline structure and zeta potential.
Aragonite performs better than calcite/limestone because of the materials high solubility
The solubility products reported by Krauskopf and Bird (1995) for calcite and aragonite indicates that aragonite is approximately 35% more soluble than calcite. Solubility testing conducted by the Keck Geophysical Laboratory at Stevens Institute of Technology in Hoboken, New Jersey indicates that in the pH range from 5-7; aragonite is significantly more soluble than calcite.
In respect to pH adjustment in the agriculture industry, aragonite’s higher solubility means that once applied aragonite has the ability to raise pH relatively quickly giving an immediate benefit to the farmer where lime may take significantly longer to achieve desired results. Additionally, farmers on the eastern shore of Maryland, Delaware, and Viginia with low pH soils have found that on average that it requires 50% less aragonite to achieve the desired pH when compared to a traditional limestone product. This is a direct result of aragonites solubility.
The unique manner in which aragonite is formed, the purity of the mineral, the exponentially greater surface area in addition to crystalline structure, zeta potential, and solubility create an unmatched competitive advantage.
Oolitic aragonite occurs naturally in seawater through a chemical and biological process. In the Bahamas, millions of tons of this mineral accumulate in vast shoals, where under certain conditions, it is accessible for commercial harvest. Oolites are ovoid or egg-shaped particles that form in agitated shallow-marine waters in tropical settings that are saturated with calcium bicarbonate. Carbon dioxide is lost to the atmosphere through degassing as a result of agitation, through elevated temperatures from solar radiation, and the activity of photosynthetic organisms. The loss of CO2 allows precipitation of calcium carbonate in the form of microscopic layers of interlocking crystals of aragonite on pre-existing skeletal or pelletoidal nuclei. Oolitic particles formed in this manner are composed of very pure calcium carbonate with unique physical properties.
Once many layers of calcium carbonate form, the oolitic particle becomes dense and falls out of suspension. In exclusive areas where conditions are right, a ridge of sand-like material will form and extend for more than 50 miles. Throughout the Bahamas more than 1 billion metric tons of material accumulate through this process, making aragonite truly sustainable, and one of the few renewable minerals in the marketplace today.
Oolitic Aragonite is generated by processing raw material and segregating a specific profile that contains only oolitic particles that can be chemically determined to be oolitic aragonite.