Ballarat rose to prominence as a goldrush boomtown, though gold no longer plays a pivotal role in the economy of the city. Nevertheless, deep underground mining continues to the present date with a single main mine operating. There are still thought to be large, undiscovered gold reserves in the Ballarat region, with investigations being made by local and national companies. Lihir Gold invested in Ballarat Goldfields in 2006, however it downscaled its operations in 2009 due to the expense of extraction before selling its stake in 2010 to Castlemaine Goldfields. Along with gold, lignite (coal), kaolin (clay) and iron ore have also been mined in the Ballarat region and nearby Lal Lal however many of the resource deposits have since been exhausted. An active quarrying industry with large enterprises including Boral Limited extracts and manufactures building materials from the Ballarat region, including clays, aggregates, cements, asphalts.