Gypsum powder is usually white, colorless, colorless and transparent crystal, which is called transparent gypsum. Sometimes it is gray, light yellow, light brown and other colors due to impurities. The stripes are white. Transparency. Glass luster, cleavage surface pearl luster, fibrous aggregate silk luster.

解理極完全，和中等，解理片裂成面夾角為66和114的菱形體。性脆。硬度1.5~2。不同方向稍有變化。相對密度2.3。石膏粉是五大凝膠材料之一，在國民經濟中占有重要的地位，廣泛用于建筑、建材、工業模具和藝術模型、化學工業及農業、食品加工和醫藥美容等眾多應用領域，是一種重要的工業原材料。

The cleavage is very complete and medium. The cleavage slices are divided into rhomboids with angles of 66 and 114. It's brittle. The hardness is 1.5 ~ 2. Slightly different in different directions. The relative density is 2.3. Gypsum powder is one of the five major gel materials. It plays an important role in the national economy. It is widely used in building, building materials, industrial molds and art models, chemical industry and agriculture, food processing and medical beauty, and so on. It is an important industrial raw material.

①取待測樣品約60g置于電熱鼓風干燥箱中，在40±4℃下烘干至恒重，將烘干后的試樣放入干燥器中冷卻備用（注：當有效干燥時間相隔1h的兩次稱量之差不超過±0.2g時，即為恒重）。

① Take about 60g of the sample to be tested and put it in the electric blast drying oven, dry it to constant weight at 40 ± 4 ℃, and put the dried sample into the dryer for cooling (Note: constant weight is defined when the difference between two weighings with an effective drying time of 1H does not exceed ± 0.2g).

稱取50±0.1g試樣置于篩內，用手指輕輕壓碎團塊，蓋上篩蓋，套上篩盤，按以下方法進行操作：一只手拿住篩，略為傾斜，搖動篩子，使其撞擊另一只手，搖動的速度為每分鐘125次，篩擺的幅度約為20cm。每搖動25次應使篩子向一定方向旋轉90度角，使試樣均勻散開（也可采用機械振動法過篩），直到篩到1min內通過篩子的試樣少于0.1g時為止，稱取篩上物質量（篩余）

Weigh 50 ± 0.1g sample and place it in the sieve. Crush the mass gently with fingers, cover the sieve cover and cover the sieve plate. Operate according to the following methods: hold the sieve in one hand, tilt it slightly, shake the sieve so that it strikes the other hand, the shaking speed is 125 times per minute, and the swing range of the sieve is about 20cm. Every 25 times of shaking, the sieve should be rotated 90 degrees in a certain direction to make the sample evenly spread (mechanical vibration method can also be used for sieving), until the sample passing through the sieve within 1 min is less than 0.1g, and the mass of the material on the sieve (sieve residue) should be weighed