THE GOLD OF THAT LAND: Biblical Minerals & Rocks  


 

34.     gypsum

    Although not specifically recognizable by name in the Bible, people in biblical times used gypsum for plastering walls and cisterns. Roasting crushed impure gypsum at 130oC drives off 75% of its water of crystallization. Mixed with lime and water, the mixture slowly crystallizes as plaster of Paris or "tempered mortar" (Ezekiel 13:10-15).

    At least a few of the many Old Testament usages of 'phr, the most generic common word for grey dust or powder, could be interpreted as roasted gypsum. Syd in Isaiah 33:12 evokes the roasting of gypsum. The plaster of Deuteronomy 27:2-3 and Daniel 5:5 is probably plaster of Paris because lime plaster required more fuel to calcine at the much higher temperature of 825oC. Examples of lime plaster use in the Holy Land date from early in the eighth millennium BC. The walls of the palace of Herod the Great at Masada were plastered with a layer of slaked lime mortar coated with plaster of Paris. The Egyptians did not use lime plaster before the Ptolemaic period, about 325 BC.

    Cisterns in Palestine and other lands of little water were symbols of peace and security. However, the broken cisterns of Jeremiah 2:13 mock the folly of choosing pagan deities instead of the Lord, the source of living water.

Mineralogy:

    Gypsum [CaSO4.2(H2O)] is the most common sulfate mineral and occurs abundantly in the Holy Land as a rock-forming and accessory mineral in sedimentary rocks. It forms monoclinic crystals in a variety of habits that make beautiful collectors' items but are too soft and delicate for use as gems and ornaments. Selenite is clear, crystalline gypsum in large masses with cleavage planes parallel to the bedding planes of the enclosing sediment. Satin spar recrystallizes in veins and fractures in sedimentary rocks, and it has a fibrous structure which gives it a silky luster. Alabaster occurs in fine-grained, massive beds. Gypsum roses or intergrown, bladed crystals grow as rosettes scattered through soft sediments in evaporitic environments.

    We use gypsum today in wallboard, plaster, and other construction materials. A small amount added to portland cement slows its setting long enough to give concrete mixers a chance to pour and form it. Powdered raw gypsum finds numerous other uses in fertilizers, fillers, insecticide carriers, and growing yeast.

Sources:

Hurlbut, 1952, op. cit.; 294.

Lucas & Harris, op. cit.; 413.

Tennisen, op. cit.; 16, 157, 398.


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Last updated: 05/13/06.