When it comes to mining, Mexico has long been associated predominantly with silver. However, gold has been mined in Mexico for at least 500 years, and the country has a history of both commercial and artisanal production. Despite that very long history of precious metals production, there are still untouched deposits in Mexico, many of which have become accessible due to recent improvements in mining technology. Gold exploration and development activity in the state of Zacatecas has increased recently for precisely that reason. Mexico's political climate is friendly to mining activity, and there is a ready supply of workers of various skill levels. Costs also tend to be favorable in comparison to other North American countries. All of those factors make Mexico a natural choice for resource exploration companies. Here are four such companies working in the country on gold exploration, development and production: GoGold Resources (TSX:GGD) GoGold Resources has several gold and silver properties in Mexico. Its Parral tailings project has 35 million ounces of silver equivalent, and the first bar has been poured. Commercial production is expected to begin in the fourth quarter of this year. The Parral Tailings project is in Hidalgo del Parral, Chihuahua, Mexico. Its Santa Gertrudis mine, which has produced gold in the past, is in Hermosillo, Sonora, Mexico. The company acquired Santa Gertrudis in April 2014 as part of its purchase of Animas Resources. Originally, the mine at Santa Gertrudis operated between 1991 and 2000, and produced 564,000 ounces of gold at an average grade of 2.13 grams per ton. It was closed as gold prices dropped. Remaining resources were until recently estimated at 557,000 ounces of gold. On July 31, however, the company announced it had drilled 21 meters of 2.22 grams per ton told in new zones at the site. This adds significant new resources adjacent to where it is already known there is available gold. GoGold continues to explore and expects the resources known at Santa Gertrudis to continue to increase.