Cabot Corp., a maker of fumed silica and carbon black that has operations in Billerica, said it has completed a $27 million fumed silica manufacturing plant in China.

The plant was developed through the company's Cabot China Ltd. subsidiary, which partnered with Blue New Chemical Materials Co. Ltd. Cabot said the facility has an annual capacity of 4,800 metric tons. Fumed silica is a material used in the creation of optical fiber for telecommunications.

Carbon black, Cabot's other specialty, is used to reinforce rubber as well as an ingredient in paints, inks and polishes. Cabot reported 2005 sales of $2.1 billion.