Golden Minerals Company is a precious metals mining company, and we own the Velardeņa Properties and associated oxide and sulfide processing plants in the State of Durango, Mexico, the El Quevar advanced exploration property in northwestern Argentina, and a diversified portfolio of approximately 10 precious metals exploration projects located in or near historical precious metals producing regions of Mexico. Our common stock is publicly traded on the Toronto and NYSE American stock exchanges.
We remain focused on evaluating and searching for mining opportunities in North America (including Mexico) with near term prospects of mining, and particularly for properties within reasonable haulage distances of our Velardeņa Properties. We are advancing our El Quevar advanced exploration silver project in Argentina, for which we have just announced completion of a positive Preliminary Economic Assessment. We are additionally focused on advancing selected exploration projects in Mexico. Our management team is comprised of experienced mining professionals with extensive expertise in mineral exploration, mine construction and development, and mine operations. Our corporate headquarters are located in Golden, Colorado, and we maintain an office in Torreon, Mexico as well as small exploration offices in Argentina and Mexico.
We have leased the oxide mill at our Velardeņa Properties to Hecla Mining Company since July 2015, and that arrangement continues to be a primary source of revenue to us as a non-producing company, having provided almost $9.5 million of net operating margin to us since its inception. The lease has been extended several times, most recently in August 2017 when Golden granted Hecla an option to secure the use of the oxide mill for an additional two years, through December 31, 2020.
Golden Minerals reported a balance of approximately $2.5 million cash and cash equivalents as of June 30, 2018, as compared to $3.3 million at December 31, 2017. The Company has no outstanding debt.
We are led by a management team with more than 60 years of combined experience in mining exploration, project development, construction and operations all over the world. Our executive officers have held senior positions at various large mining companies including, among others, Cyprus Amax Minerals Company, INCO Limited, Meridian Gold Company, Barrick Gold Exploration and Noranda Exploration. Our executive team has a proven ability to manage large projects in challenging environments.