China clay is also known as kaolinite a common phyllosilicate mineral having the chemical name aluminum silicate hydroxide- Al2Si2O5(OH)4. The name kaolinite is derived from the Chinese word gaoling or kaoling. It is a layered silicate mineral which is bonded to aluminum oxide layers called gibbsite layers. Silicate and gibbsite layers are tightly bonded together with only weak bonding exists between them is causes the cleavage and softness of the mineral. Natural China clay contains small amounts of uranium and thorium.
OCCURENCES AND DEPOSITS
A primary constituent of clay beds formed by the decomposition of feldspar-bearing rocks. Rocks that are rich in kaolinite are known as china clay, white clay, or kaolin. China clay is abundantly available in Jianxi China, Macon Georgia USA, Huberdeau, Quebec, and near Walton, Nova Scotia Canada.
· Color is white, greenish or yellow sometimes brown and even colorless.
· Crystal system is triclinic 1.
· Streak is white.
· Crystal habit is thin platy or stacked, foliated and aggregated into compact claylike masses.
· Cleavage is perfect in one direction.
· Luster is pearly to dull earthy.
· Hardness is 1.5 to 2.
· Specific gravity is 2.6 g/cm3.
· Kaolinite is translucent.
· China clay is used as filler for paint, rubber, plastics since it is inert and long lasting.
· It has vast use in the production of paper, including ensuring the gloss on some grades of paper.
· In organic farming China clay is used to spray on crops to deter insect damage.
· Since it contains traces of uranium and thorium it is being used in radiological dating.
QUESTION AND ANSWERS
1. Write the chemical name and formula for Chinaclay or kaolinite?
Ans: It has the chemical name as aluminum silicate hydroxide- Al2Si2O5(OH)4.
2. Mention 2 properties of China clay?
Ans: Color is white, greenish or yellow sometimes brown and even colorless.
Luster is pearly to dull earthy.
3. Give some applications of China clay?
Ans: It has vast use in the production of paper, including ensuring the gloss on some grades of paper.
In organic farming China clay is used to spray on crops to deter insect damage.