Brief introduction of clay
The term clay refers to a number of earthy materials that are composed of minerals rich in alumina,silica and water.Clay is not a single mineral.But a number of minerals.When most clays are wet,they become “plastic” meaning they can be formed and molded into shapes.When they are “fired” (exposed to very high temperatures)the water is driven off and they become as hard as stone.Clay is easily found all over the world.As a result,nearly all civilizations have used some form of clay for everything from bricks to pottery to tablets for recording business transactions.
Application of clay
Ball clays are good quality clays used mostly in pottery but are also added to other clays to improve their plasticity.Ball clays are not as common as other clay varietiesOne third of the ball clay used annually is used to make floor and wall tilesIt is also used to make sanitary warepotteryand other uses.
Bentonite is formed from the alteration of volcanic ashBentonite is used in pet litter to absorb liquidsIt is used as a mud in drilling applicationsIt is also used in other industrial applications such as the “pelletizing” of iron ore.Common bentonite is used to make construction materials such as brickscementand lightweight aggregates.
Fire clays are all clays (excluding bentonite and ball clays) that are used to make items resistant to extreme heatThese products are called refractory productsNearly all (81%) of fire clays are used to make refractory products.
Fuller’s earth is composed of the mineral palygorskite (at one time this mineral was called “attapulgite”)Fuller’s earth is used mostly as an absorbent material (74%)but also for pesticides and pesticide-related products (6%).
Kaolinite is a clay composed of the mineral kaolinIt is an essential ingredient in the production of high quality paper and some refractory porcelains.
Distribution of clay
Clays are common all over the worldSome regionsas might be expectedproduce large quantities of specific types of clayIt is estimated that the state of Georgia has kaolin clay reserves of 5 to 10 billion tonsThe United States is self-sufficient so it imports only small amounts of clay from MexicoBrazilUnited KingdomCanadaand assorted other nationsThe United States exports nearly half of its production worldwide.
The nations producing the most significant amounts of the various clays are as follows:
- Kaolin: BrazilUnited Kingdomand the United States are the dominant producers of high quality kaolin.
- Ball clays: Major producers of ball clays are Germanythe United StatesUnited Kingdomthe Czech RepublicChinaand France.
- Fire clays: Major fire clay producing countries are Germanyand the United States.
- Bentonite: Major producers of bentonite are the United StatesGermanyTurkeyand Greece.
- Fuller’s earth: Major producers of fuller’s earth are the United States (attapulgitesmectite)Spain (attapulgitesepiolite)and Senegal (attapulgite).