mica

Mica has a high dielectric strength and excellent chemical stability, making it a favored material for manufacturing capacitors for radio frequency applications. It has also been used as an insulator in high voltage electrical equipment. It is also birefringent and is commonly used to make quarter and half wave plates. Because mica is resistant to heat it is used instead of glass in windows for stoves and kerosene heaters. Illites or clay micas have a low cation exchange capacity for 2:1 clays. K+ ions between layers of mica prevent swelling by blocking water molecules. Aventurine is a variety of quartz with mica inclusions used as a gemstone. Pressed Mica sheets are often used in place of glass in greenhouses. In 2003 China was the leading exporter of mica, accounting for 26％ of all exports measured by quantity. In 2003 Japan was the leading importer of mica, accounting for 22％ of all imports measured by quantity. Global Mica production is expected to increase 3％ from 2006 to 2008.