Gypsum (CaSO4· 2H2O) is a soft white, grey, brownish or slightly pink mineral consisting of hydrated calcium sulphate also know as calcium sulphate di-hydrate. It occurs mainly in sedimentary deposits and is used to for soil amelioration and in building construction materials.
Gypsum is moderately water-soluble (~2.0–2.5 g/l at 25 °C) and, in contrast to most other salts, it exhibits retrograde solubility, becoming less soluble at higher temperatures.
Gypsum is generally found in mineral and rock form, but there is also recycled, synthetic and byproduct forms of gypsum. Mined gypsum is a very soft mineral and it can form very large colored crystals. Natural gypsum is found in many parts of the world. Gypsum deposits lie in flat beds of about six to eight feet in thickness, and are often inter-layered with limestone or shale. Gypsum deposits were formed millions of years ago when salt water oceans covered most of the earth, and as they receded, may inland “dead” seas were formed which, as evaporation continued, became more and more salty. As those salts precipitated, they formed various compounds in turn, one of which was gypsum. As millions of years passed, these salt deposits combined with decayed vegetation and other minerals, and eventually the result was stratified rock, with layers of gypsum and layers of limestone alternating, the whole covered over with many feet of glacial deposits. The result is the accumulation of large beds of sedimentary gypsum near old salt lakes and inland river beds.
The main types of gypsum in the market place for agricultural, civil and industrial application are:
Natural gypsum: is mined from the ground as a mineral and sold for industrial, medical and agricultural uses. Generally the mined gypsum will be selenite gypsum which is an opaque sandy crystal gypsum. There are various grades of mined gypsum and it is essential you determine you are getting the best bang for your buck. The easiest method of comparison is gypsum purity or each gypsum source available to you.
Recycled Gypsum: is derived from plasterboard waste and is a high quality source of gypsum. The product has a granular feel making it easier to spread. The granules porous structure increases the surface area making the recycled gypsum more soluble. Read more.
Synthetic gypsum (Not Sold by PacFert): industrial gypsum, FGD (Flu Gas Desulphurised Gypsum) and DSG (Desulphurised Gypsum) are all names for gypsum which are created by through chemical processes and not mined virgin product. Synthetic gypsum is most typically created in scrubbers, using lime (Ca), in coal fired power plants to clean the sulphur (SO) from the smoke stacks. The lime and sulfate combine and make synthetic gypsum (CaSO4· 2H2O) which is a high quality and very pure gypsum material. Chemically this gypsum is identical to natural gypsum.
Phosphogypsum (Not Sold by PacFert): refers to the gypsum formed as a by-product of processing phosphate ore into fertilizer with sulfuric acid, such as Phosphate Hill in Central West QLD. REGYP DOES NOT SELL Phosphogypsum in Australia. Phospho gypsum is produced from the fabrication of phosphoric acid by reacting phosphate rock with sulfuric acid. Phosphogypsum does contain moderate levels of heavy metals including cadmium and REGYP recycled gypsum products DO NOT, so the two should not be confused. Phosphogypsum is radioactive due to the presence of naturally occurring uranium and radium in the phosphate ore. Marine-deposited phosphate typically has a higher level of radioactivity than igneous phosphate deposits, because uranium is present in seawater.
Comparing Gypsum Products: Please follow the link for a complete gypsum comparison report.
