Aztec chases silver-zinc deposits at Tombstone

Aztec Minerals (TSXV: AZT; US-OTC: AZZTF) has started surface exploration at its newly optioned Tombstone silver-zinc district, 104 km southeast of Tucson, Arizona. The company is chasing multiple mineralization types, but mostly carbonate-replacement deposits — like at South32’s recently acquired Taylor zinc project, 65 km southwest of Tombstone in southern Arizona.

Tombstone is the second project for the relatively new company. It controls nearly all the historic, patented land in the district.

In an interview with The Northern Miner, Aztec chairman Brad Cooke says there are dozens of old mines on Aztec’s ground.

“Even though we’re just starting, Tombstone has a tremendous amount of history and some real obvious targets,” Cooke says.

The company aims to refine targets for a first round of drilling. The first phase of work at Tombstone includes $139,000 of mapping, soil and rock sampling, trenching and airborne geophysical surveying.

The company is interested in two mineralization styles.

The first style is an epithermal mineralization found at the district’s biggest past producer: the old open-pit, heap-leach Contention gold-silver mine. Cooke says the company believes the old mine still has “quite significant upside.”

Aztec found historic drill data sets that may support this belief. In the early 1990s, USMX drilled 6,100 metres in 63 holes and MPV Capital drilled 1,900 metres in 14 holes in areas that were never mined. Aztec intends to release those results in mid-September, after they are verified.

The Tombstone project near Tuscon, Arizona. Credit: Aztec Minerals.

The company also has a 1993 historic resource by USMX that outlines 1.15 million near-surface tonnes grading 1.79 grams gold per tonne.

“But by far the bigger opportunity is what we call carbonate-replacement deposits below the historic mines and below the Contention pit,” Cooke says. “We are looking at what we would call a Taylor deposit lookalike.”

South32 recently acquired Taylor when it bought Arizona Mining for US$1.3 billion. Taylor is a carbonate-replacement, massive sulphide deposit that contains 91.5 million measured and indicated tonnes grading 4.3% lead, 4.1% zinc and 59.5 grams silver, or 10.4% zinc equivalent.

Previously named Wildcat Mining, Arizona Mining had focused on a historic silver mining camp called Hermosa. When it ran into metallurgical problems, it shifted its focus from silver to zinc, chasing a historic hole on the property. The hole led to Taylor, lying below the silver district.

“Tombstone looks remarkably similar,” Cooke explains. “We have a historic district up in a particular rock formation. The rock formation is only 200 metres thick and then there’s an unconformity, and you’re down into the same host Paleozoic limestone at Tombstone that hosts the Taylor deposit.”

An explorer stands beyond historic mining zones at the Tombstone district. Credit: Aztec Minerals.

Cooke notes that none of the historic mines at Tombstone were able to process any significant mineralization. At Contention, for example, the operators hit sulphides in the late 1800s and early 1900s, but didn’t have the technology to extract metals from them.

Although its mineral prospectivity remains to be proven, the Tombstone district is rich in American frontier lore.

In the mid-1800s, the American army sent groups of scouts to the area looking for Native Americans. One scout, Ed Schieffelin, joined so he could prospect the area part-time.

When his army friends found out what he was doing, they told Schieffelin:

“The only rock you’ll find out there will be your own tombstone.”

So the story goes, at least.

Apaches attacked Schieffelin and his party, forcing them into hiding. Schieffelin used the time to prospect, and eventually left the army. He found a silver vein and staked a claim — right next to the grave of a scout killed in the Apache attack.

Schieffelin brought samples of his claim across the state to the McCracken mine in Signal City, Ariz., where his brother Al worked. He got them assayed by a man named Richard Gird. The two brothers and Gird later formed a business partnership when the samples were found to grade high in silver.

From 1878 to 1939, the Tombstone district produced an estimated 32 million oz. silver.

Aztec expects to finish its first phase of exploration by September and release results in October. It will soon begin two weeks of trenching. Because the property is patented land, the company does not need permits to begin trenching.

The Cervantes project in Sonora, Mexico, is currently under option by Aztec. Credit: Aztec Minerals.

Aztec optioned the Tombstone properties from Baroyeca Gold & Silver (TSXV: BGS) in late 2017. The properties total 1.6 sq. km of patented claims and another 0.09 sq. km of unpatented claims.

Aztec can acquire a 75% interest in the district by spending $1 million on exploration, issuing Baroyeca 1 million shares and paying Baroyeca $100,000 over three years.

Aztec went public last May with only its Cervantes gold-copper project in Sonora, Mexico, under option from Kootenay Silver (TSXV: KTN; US-OTC: KOOYF), as a substantive asset.

“We used a chunk of the initial public offering money last year and this year to do the phase-one drilling at Cervantes,” Cooke says. “And we had some pretty nice results.”

The company defined porphyry-type copper-gold mineralization at Cervantes over 800 metres. Highlights include 160 metres from surface grading 0.77 gram gold, 0.13% copper and 3.4 grams silver, as well as 98.5 metres from surface at 0.41 gram gold, 0.13% copper and 2.2 grams silver.

In March, the company expanded its land package at Cervantes sixfold when it won two concessions totalling 31.5 sq. km in a Mexican government land lottery. It’s wrapping up a phase-two surface exploration program at Cervantes now.

The company is studying the  leaching characteristics of the Cervantes core and aims to announce those results by November.

It’s also pursuing an acquisition.

Next year, it will look to drill more, including a third phase of drilling at Cervantes.

Shares of Aztec are trading at 22¢ with a 52-week range of 14¢ to 38¢. The company has a $6-million market capitalization.

“We’re very excited by the opportunity to identify and ultimately drill Taylor lookalike targets at Tombstone,” Cooke says.