Soil h2o potential checking: a gypsum block may be inserted into the soil, and its electrical resistance can be calculated to derive soil humidity.[48] Crystal Technique: Gypsum crystals belong on the monoclinic crystal system. This crystal framework has three unequal axes, with just one angle between axes remaining non-90 degrees. https://www.propanraya.com/id/produk/eco-gypsum-ee-4050