Canadian uranium miner Hathor Exploration Ltd. is urging its shareholders not to respond to an unsolicited takeover bid by Cameco Corp., a larger Canadian uranium producer that is offering to buy Hathor in an all-cash deal worth $531 million.

Cameco Corp., which is based in Saskatoon, Saskatchewan, is offering $3.75 (Canadian) per share of Hathor, whose stock closed Monday at $3.95.

Hathor explores for uranium in the Athabasca Basin of northern Saskatchewan. Its most significant asset is the Roughrider uranium deposit, which is near a Cameco mill and holds indicated and inferred resources of about 17.2 and 40.7 million pounds of uranium, respectively .

Hathor believes the offer from Cameco is opportunistic, leveraging the market capitalization set-back in this industry post-Fukushima, and announced just prior to Hathor's planned release of the first economic assessment of the Roughrider uranium deposit, anticipated in mid-September, the company said Monday in a statement. Hathor's closing share price was a material premium to Cameco's offer on the day Cameco announced its intent.

Cameco said its offer price of $3.75 per Hathor share represents an attractive premium of 40 percent over Hathor's closing price and 33 percent over Hathor's 20-day volume-weighted average price as at Aug. 25, 2011.

The market has recognized the exceptional job Hathor has done with the Roughrider deposit and the company's other properties, Cameco said in a statement. Given our financial strength, development expertise, existing infrastructure and experience in the Athabasca region, we feel we are in a unique position to build on that success and further advance the Roughrider deposit.