Precious Metals

Stripping Gold & Silver from Carbon – Chemistry

Stripping of gold and silver from carbon is effected by means of two main processes (AARL and ZADRA). The main rate-enhancing parameter in the stripping of gold and silver is temperature. A secondary rate-enhancing parameter is ionic strength. (1) Stripping is usually conducted within a solution containing sodium cyanide (0.1 – 0.5%) and caustic (1 … Read more

How to turn Dust into Gold

The primary metals sector was particularly hard hit early on, to develop the technology, acquire the equipment, and implement the programs to eliminate or reduce the by-products of metal making. To this end, through a combination of technological innovation and extensive capital expenditures, the metals industry has net, and in many cases, exceeded the minimum … Read more

How to Extract Precious Metals from Geological Brines

It is now well documented that trace amounts of silver, gold, and platinum group metals occur in certain geothermal brine deposits. A significant body of literature has been generated over the last twenty years which describes attempts to quantify the frequency and levels of these precious metals in the brines. There are numerous reports of … Read more

Merrill-Crowe Plant Design Factors

The removal of metal values from cyanide solutions, fortunately, can be done in several ways. The oldest practiced method is, cementation with zinc, or Merrill-Crowe. The original patent for recovery of gold and silver from cyanide solutions described precipitation with zinc dust. Most early practitioners, however, used granules of zinc in a successful attempt to … Read more

Soda Ash Roasting of Antimony & Arsenic Gold Concentrate

The ability to process complex precious metal sulfide concentrates containing antimony and arsenic, in an economic and environmentally safe manner, is an important problem facing the mining industry in the United States. Preliminary experiments have been performed to evaluate the possibility of treating a complex sulfide concentrate to recover antimony and precious metals while fixing … Read more

Precious Metal Recovery Methods

Process Selection Trends A general trend in precious metals extraction technology has been the treatment of ores with progressively lower grades. The lowest cost treatment, dump leaching of material at run-of-mine size, has been increasingly applied. For example, Zortman-Landusky (Montana) is successfully leaching material above a cutoff grade of 0.2 g/t (0.006 oz/ton) at an … Read more

Gold Milling Operations at Snip Mine

Exploration and staking in the area commenced as early as 1929. The original Snip showing was located by Cominco geologists in 1965. The property changed hands in the 1970’s but was reacquired by Cominco in 1980 only to be optioned to Delaware Resources cum Prime Resources in 1986. Exploration drilling and underground sampling from 1986 … Read more

Puerto Rico Mining & Precious Metal Mineralization

Mining has never been a major source of income for Puerto Rico. The Spaniards mined gold placer deposits during 1509-1579, and extracted an estimated 1,200,000 troy ounces of gold. However, economics at the time discouraged further mining, and richer sources of gold and silver had been found elsewhere in the New World. The labor source, … Read more

Carbon Adsorption of Silver from Acidified Thiourea Solutions

Carbon adsorption was considered as the most adequate method for recovery of silver from thiourea leach solutions. For this reason it was decided to examine the characteristics of adsorption of silver on activated carbon. Coconut hard shell activated carbon was used for this study. Experimental The carbon, coconut hard shell, was pulverized and dry seived … Read more

How Metal Impurities Affect Gold Adsorption on Activated Carbon in Cyanide Solutions

We performed batch equilibrium contact experiments to examine the ability of activated coconut-shell carbon to adsorb various metal cyanide complexes. Tests were also conducted to determine the effect these cyanide complex impurities might have on the adsorption of gold by the activated carbon. Metal cyanide species included in the investigation were antimony, arsenic, cadmium, calcium, … Read more