Older excerpt from a Newmont website:
"Underground mining, in higher-grade ore down-dip from existing open pits, started in 1994, with two extensions from Carlin. Rain, which works oxide ores by longhole stoping, is an extension of the depleted Rain pit, and Deep Star is an extension from Genesis. Deep Post, which started up in 2001 and produced 227,000oz in its first year, has its portal located within Barrick Goldstrike's Betze/Post open pit.
In 2002, development began on the 700m-deep Leeville deposit, which has reported reserves of 2.7Moz, with ore hoisting scheduled to start by mid-2006 and to reach 1900t/d by end-2006: full-rate gold output should be 500,000–l550,000oz/y for more than eight years. Newmont is using MineStar to help manage its Nevada operation."
"ORE PROCESSING
The process plants available, some using Newmont proprietary technology, provide considerable flexibility: a linear programme helps to direct ore types to the plant offering the highest economic return. Newmont groups its Nevada process units as follows:
Oxide mills: Carlin Trend mill 5; Midas, Twin Creeks; Lone Tree
Refractory mills: Carlin bio-leach (mill 5), Carlin roaster (mill 6); Lone Tree flotation, Twin Creeks and Lone Tree autoclaves
Dump Leach operations: Carlin-oxide, Carlin-refractory; Twin Creeks and Lone Tree oxide
Although Newmont processes several ore types, the proportion of gold recovered from refractory ores rose from 30% in 1996 to 66% in 2002."
From Granview website:
"There are two types of Carlin systems; the shallow systems where lower grade gold occurs as dissseminations in carbonaceous, limey siltstones and altered limestone and is spread out over a cloud of mineralization at depths of 500-700 feet. These shallow systems are developed as open pit mines with lower cost production. Open pit mines remain the major source of Carlin Trend ore.
Deeper, higher-grade sulfide gold mineralization commonly occur at depths below 1,000 feet. These deeper systems are developed as underground mines and involve higher cost production. Rain and Goldstrike began as open pit mines and developed to include underground mines.
Grandview's 28 square-mile Pony Creek/Elliott Dome property is being explored for both open pit and underground mining potential over three primary target areas - Pony Creek West, Red Rock and Pony Creek South, and several proximal areas. A comprehensive drilling program is underway. Check the Company News pages of this website for recent news or visit Pony Creek Drilling Results for more information."
