Gran Colombia Gold Corp., the largest underground gold and silver producer in Colombia, said Tuesday it posted a net loss in the second quarter of $11 million, or 4 cents per share, after a one-time charge on its merger with Medoro Resources Inc.

In the first six months of this year the company lost $27.7 million, or 12 cents per share, as a result of a one-time charge stemming from the Medoro merger and a charge related to a Colombian tax.

Revenues in the April through June quarter were 27.8 million, principally from the sale of 17,533 ounces of gold at an average realized price of $1,529 per ounce.

For the first half of 2011, gold sales amounted to 32,307 ounces and total revenues were $48.5 million.

Gran Colombia runs six underground mines in Colombia and is developing a large-scale, open-pit gold and silver mine at Marmato.