BHP Billiton’s informal takeover offer for mining rival Rio Tinto may be the biggest takeover deal on the cards, but locally there is plenty of action among small and mid-cap mining companies. A friendly takeover by CopperCo of Mineral Securities this week joined the long list of Western Australian mining takeovers. CopperCo plans to acquire MinSec through a recommended scrip offer that values the target at $149 million. The merged group will have interests in base and precious metals and a market value of $530 million. Assuming the deal is completed, Minsec will join Consolidated Minerals, Jubilee Mines, and Kimberley Diamonds as WA companies to have disappeared from the bourse. Herald Resources is also likely to fall to an offer from Indonesian company PT Bumi Resources, though the Herald board is still scouting for competing offers. Fairstar Resources’ hostile takeover offer for Golden West Resources shows that takeovers can take the most unexpected turns. Golden West’s major shareholder, Falak Holdings, which has vigorously opposed the takeover offer, was shocked to discover that its custodial agent had mistakenly issued instructions to accept the offer. The companies have launched an investigation.