Silver Bull Resources (TSE:SVB)(NYSE MKT:SVBL) has unveiled its updated resource estimate for its Sierra Mojada project in Mexico, saying it “significantly increased” both the size and grade of the silver resource. 

Shares of the junior silver and zinc explorer advanced more than 5 percent this morning, to trade at 38.5 cents in Toronto. 

Last year, the company undertook an underground drill program that twinned what Silver Bull calls a historical “long hole” data set along a high grade silver zone and an underlying and adjacent high grade zinc zone – both located at the eastern end of previous resource. 

The aim of the campaign, which concluded in December, was to increase confidence in the historical data, which represented 39,000 metres of drilling that was either “severely restricted” or discarded in the company’s prior NI 43-101 resource report on the Shallow Silver zone in July of last year.

Based on the results of the 6,500 metre program, the updated report, at a 25 grams per tonne (g/t) cutoff grade, now shows an indicated silver resource of 71.9 million tonnes at a grade of 72.5 g/t silver, for 167.5 million troy ounces. 

The NI 43-101 compliant report, done by JDS Energy & Mining, also shows an indicated zinc resource of 2.19 billion pounds, at an average grade of 1.38% zinc. 

Inferred resources for both lead and copper were also calculated, with 538 million pounds of lead at a grade of 0.34% and 126 million pounds of copper at an average grade of 0.08%. 

The company said Monday that at the 25 g/t cutoff grade for the silver, the updated resource is more than double that of the open pittable resource of the Shallow Silver zone from last July. 

The additional data used in the most recent estimate includes more than 10,000 metres of surface diamond drilling, over 6,600 metres of underground diamond drilling, and roughly 400 new channel samples. 

“We are extremely pleased with this report and feel this is a big step forward for the company,” Silver Bull said in its statement Monday, citing president and CEO, Tim Barry. 

“At over 167 million ounces, Sierra Mojada is now one of the largest undeveloped silver resources in Mexico. With our recently completed financing for gross proceeds of $USD 9.2 million, the company is well financed to push the project to the next stage with a preliminary economic assessment, which will be led by JDS.” 

Barry went on to say that “it is no small point” to note that even though the company defined a much larger resource than previously reported, mineralization at the deposit remains open. 

This year, another underground program will take place, using its termite drill rigs that will target a high grade silver zone defined by underground channel samples just next to the deposit. 

For the past months, Silver Bull has released a series of high grade silver and zinc results from its underground program last year, with some notable holes such as 912 g/t silver over 17.6 metres, including 1,927 g/t silver over 3.66 metres. Some high grade zinc intercepts included 19.52% zinc over 22.85 metres. 

Vancouver-based Silver Bull’s Sierra Mojada project is located 150 kilometres north of the city of Torreon in Coahuila, Mexico. The Shallow Silver Zone is an oxide silver deposit that averages between 30 to 90 metres thick, and is up to 200 metres wide, remaining open in the east and west directions. 

The company also owns two mineral exploration licences in Gabon, Africa, which are prospective for gold, manganese, and iron ore.