are kaolinitic sedimentary clays
, that commonly consist of 20-80% kaolinite
, 10-25% mica
, 6-65% quartz
. Localized seam
in the same deposit have variations in composition, including the quantity of the major minerals
, accessory minerals and carbonaceous
materials such as lignite
. They are fine-grained and plastic in nature.
Ball clays are relatively scarce deposits due to the combination of geological factors needed for their formation and preservation. They are mine
in parts of the Eastern United States and from three sitesThe Bovey Basin
in South Devon, the Petrockstowe Basin in North Devon and the Wareham Basin in South Dorset. in Devon
in South West England
. They are commonly used in the construction of many ceramic articles, where their primary role is to either to impart plasticity or to aid stability during the shaping processes.
The name "ball clay" is believed to derive from the time when the clay was mined by hand. It was cut into 15 to 17-kilogram cubes and during transport the corners of the cubes became rounded off leaving "balls".
use of ball clays in Britain
dates back to at least the Roman
era. More recent trade began when a clay was needed to construct tobacco pipes
in the 16th and 17th century. In 1771 ... Read More