The Barrick Gaming Corporation said that it is buying a casino, the Golden Nugget Laughlin, for $31 million from the Poster Financial Group. Earlier this year, Barrick, which is based in Las Vegas, bought the Plaza, Las Vegas Club, Western and Gold Spike for about $82 million. Barrick also acquired the downtown Queen of Hearts and Nevada hotel-casinos in October. The Poster Financial Group said the sale would allow his company to focus on its primary asset, the Golden Nugget Las Vegas, on the Las Vegas Strip. The Golden Nugget Laughlin is part of a string of hotel-casinos on the Colorado River, about 100 miles south of Las Vegas.