Beryllia has been produced commercially for over fifty years. It shows a high thermal conductivity, yet also has a high volume resistivity and used typically as an electronically insulating heat sink. Beryllia has a high dielectric strength and a low dielectric constant. It exhibits good thermal shock resistance and is chemically stable up to 2000C. This leads to use for crucibles and thermocouple tubes. It has a low density, high strength and high hardness and is transparent to microwaves. The processing of this highly toxic material has been controlled for 30 years, although it may be handled safely provided the correct procedures are followed.