Gypsum - Gypsum

Japanese: セッコウ(石膏) - せっこう

The mineral name of naturally occurring calcium sulfate dihydrate, CaSO ₄・2H ₂ O. It has monoclinic columnar or plate-shaped crystals with a hardness of 2 and a specific gravity of 2.32. It is colorless, sometimes colored gray, yellow, or red by impurities. It is transparent or translucent. It is the most abundant sulfate mineral, forming large sedimentary layers and associated with rock salt, sulfur, and black ore deposits. When heated, it loses some of its water of crystallization to become anhydrite (calcined gypsum). It is used as a Portland cement setting retarder, a filler for paper and rubber, and a pigment. Lumpy alabaster, consisting of an aggregate of fine crystal particles, is used for decoration and sculpture.
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Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

天然に産する硫酸カルシウム２水塩CaSO₄・2H₂Oの鉱物名。単斜晶系の柱状または板状結晶で，硬度２，比重2.32。無色，ときに不純物により灰，黄，赤に着色。透明ないし半透明。最も多量に産出する硫酸塩鉱物で，大きな堆積層をなし，岩塩，硫黄，黒鉱鉱床などに伴う。加熱により結晶水の一部を失い硬セッコウ（焼セッコウ）となる。ポルトランドセメント凝結遅緩材，紙・ゴムの充填(じゅうてん)材，顔料などに使用。微結晶粒子の集合体からなる塊状の雪花セッコウ（アラバスター）は装飾用，彫刻用。
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