The joint facility owned by Apple and GT Advanced Technologies in Mesa, Arizona is expanding, said Apple Insider. The number of buildings and facilities on the 83-acre plot of land is growing, perhaps to accommodate higher yields for products yet to be announced. 

Called Project Cascade, the joint manufacturing facility focuses on the production of synthetic sapphire which is used in watches, solar cells, and possibly future iPhones. The factory sits on 83-acres of land, which is mainly taken up by the main structure of the facility. The rest of the area is composed of parking lots, support structures, and various equipment. The purpose of the second structure current being built is still unknown. It is rumored however that there will be a total of 1700 sapphire growth furnaces in the facility to produce sapphire in bulk. 

Apple planned for the facility to be operational by February. Although still under construction, parts of the facility are operational and churning out product, according to Apple Insider. The plant is currently powered by temporary generators. Construction is planned to be complete by June. 

The purpose of the plant is still unknown. Some speculate that it could be to produce sapphire display covers for upcoming iPhones. However, the plant could have been established to simply supply the sapphire for use in Touch ID sensors and lens covers. Apple is staying tight lipped about their future plans with sapphire.