The International Cyanide Management Code for the Manufacture, Transport and Use of Cyanide in the Production of Gold, commonly referred to as the Cyanide Code, is a voluntary program designed to assist the global gold and silver mining industries and the producers and transporters of cyanide used in gold and silver mining in improving cyanide management practices and to publicly demonstrate their compliance with the Cyanide Code through an independent and transparent process. The Cyanide Code is intended to reduce the potential exposure of workers and communities to harmful concentrations of cyanide‚ limit releases of cyanide to the environment‚ and enhance response actions in the event of an exposure or release.
The Cyanide Code was one of the earliest standards and certification programs developed for the minerals sector. Today, it is among the most established certification programs in the mining industry.
As a result, the Cyanide Code has been used as a model in the development of other standards initiatives, including the Global Industry Standard on Tailings Management.
The program's audit process and the transparency of audit results set it apart from other voluntary industry programs.
Cyanide in gold mining
Cyanide is a general term for a group of chemicals containing carbon and nitrogen. Cyanide compounds include both naturally occurring and human-made chemicals. In nature, cyanide is present naturally in plants including bitter almonds, apples, peaches, apricots, lima beans, barley, sorghum, flaxseed and bamboo shoots. Some scientists suggest that the reason why these plants contain cyanide, which can be toxic, is that evolution has designed them to discourage insects from feasting on them. Although cyanide can be toxic to humans, eating cyanide-containing foods generally is not harmful because cyanide is present in very low amounts, is often contained in seeds which are discarded, or is washed away when the food is prepared. Cyanide can be acutely toxic to humans, other mammals and aquatic species, as it interferes with oxygen utilization. Cyanide does not bioaccumulate, and a non-lethal dose is metabolized in the body. Cyanide is not carcinogenic, teratogenic or mutagenic.
Cyanide comes in many forms including hydrogen cyanide (HCN), cyanogen chloride (CNCl), and salts such as sodium cyanide (NaCN) or potassium cyanide (KCN). In manufacturing, cyanide is used to make paper, textiles, and plastics. Cyanide salts are used in metallurgy for electroplating, metal cleaning, and removing gold from its ore. Cyanide gas is used to exterminate pests and vermin in ships and buildings.
Cyanide is a basic building block for the chemical industry. About 80% of global cyanide production is used to synthesize a wide range of industrial organic chemicals such as nylon and acrylics.
It is estimated that less than 20% of manufactured cyanide is used in mineral processing in the form of sodium cyanide. Sodium cyanide has been used in gold mining since 1887 because it is one of only a few chemical reagents that will dissolve gold in water. This allows the efficient extraction of gold from low grade ore. Commercial gold mining operations use very dilute solutions of sodium cyanide, typically in the range of 0.01% and 0.05% cyanide (100 to 500 parts per million).
Cyanide should be strictly controlled on mine sites, and proper management requires that certain precautions be taken to limit worker exposure and to prevent chemical solutions containing cyanide from entering the environment. The most-used process of removing gold from ore is through leaching. In the leaching process, sodium cyanide is dissolved in water where, under mildly oxidizing conditions, it dissolves the gold contained in the crushed gold ore. The resultant gold-bearing solution is called 'pregnant solution.' Either zinc metal or activated carbon is then added to the pregnant solution to recover the gold by removing it from the solution. There are two main leaching methods for gold extraction using cyanide. The first is 'heap' leaching in which the dilute cyanide solution is sprayed on large piles or heaps of coarse gold ore. The solution percolates through the pile dissolving the gold and the pregnant solution is then collected. This method is mainly used for ore with lower concentrations of gold. The other method is 'vat' leaching in which the process is similar but the gold ore is finely ground and leaching takes place in a tank or vat. Vat leaching is used mainly for ores with higher concentrations of gold due to the cost of milling the ore to a very small particle size. Alternative lixiviant (leaching) chemicals to cyanide (for example thiourea, sodium bromide) have been investigated for many years, but they are generally less effective and/or economical than cyanide, and they also present environmental risks that can be greater than cyanide. Because cyanide is toxic if not properly handled, its use is highly regulated in most countries.
Despite regulatory and voluntary safeguards, however, some jurisdictions have banned its use in gold mining. These include Slovakia, the Czech Republic, Germany, and Hungary. Several provinces in Argentina also prohibit the use of cyanide in mining. In the U.S., the state of Montana has taken action to ban cyanide in gold production.
History
Cyanide, a highly toxic chemical, has been the most widely used reagent for extracting gold from ore for the past century. The Cyanide Code grew out of the first-of-its-kind workshop of multi-stakeholders held in Paris in May, 2000 convened to consider developing a code of best practice for the use of cyanide in gold mining in response to a tailings spill from the Aural Mine at Baia Mare in Romania in January 2000. The meeting was co-hosted by The United Nations Environment Programme (UNEP) and the International Council on Metals and the Environment (now the International Council on Mining and Metals). Workshop participants were almost 40 representatives of such diverse organizations as the Worldwide Fund for Nature, the Mineral Policy Center (now Earthworks), the Sierra Club, and the World Gold Council, along with representation from the U.S. Environmental Protection Agency, the governments of Australia, France, Hungary, Romania, and the world's leading gold producers and cyanide producers.
As a result of the workshop, a multi-stakeholder steering committee was established to oversee development of a code of best practice for the management of cyanide used for gold recovery. The committee met five times over a 13-month period starting in late 2000, and each successive draft of the best practice document it produced was made available to the public on the UNEP web site with an open invitation for comments. The committee also solicited comments directly from 140 groups and individuals, including governments, NGOs, academics, consultants, industry, and financial institutions, and received 68 written responses and 15 stakeholder presentations at its meetings. In early 2002, the committee completed the International Cyanide Management Code for The Manufacture, Transport and Use of Cyanide In The Production of Gold.
As conceived by the steering committee, the Cyanide Code was more than a guide to best management practices for the use of cyanide in the production of gold. The Cyanide Code also addressed the safe manufacture and transport of the cyanide used in the gold industry. Further, although the program is voluntary, the Cyanide Code includes a process by which its implementation at gold mines and other facilities is verified by independent third-party professional auditors and audit results are made available to the public. The International Cyanide Management Institute (ICMI) was established in 2003 to oversee the Cyanide Code's implementation and verification, and by 2005, the administrative procedures, audit protocols and guidance documents necessary for full program implementation had been developed.
2015 marked the tenth year of implementation of the Cyanide Code globally.
In 2017, the International Cyanide Management Institute undertook a public consultation process to determine if the Cyanide Code should be extended to include primary silver mines, which is defined as an operation where silver is the main commodity produced. About 30% of the world's silver production comes from primary silver mines; the balance is produced as a co-product from polymetallic, base metal, or gold mines. The Institute solicited input from stakeholders on the proposal, including its advisability, policy or technical issues, and any other related matters. Following receipt of stakeholder comments, all of which were supportive of the change, ICMI's Board of Directors approved the program's expansion, effective January 1, 2017.
The Cyanide Code is supported by a suite of documents that provide guidance and instructions to participating operations in preparing for certification and to auditors in assessing compliance. They also provide information, instruction, and details on administrative requirements for participating companies and auditors. In 2019, ICMI initiated a process to undertake a comprehensive review and updating of the Cyanide Code's supporting documents following a public consultation. The objective of the review was four-fold: 1) accounting for changes in industry practices since initial development of the Cyanide Code and its supporting documents; 2) addressing gaps and "soft spots" in requirements for auditing and compliance; 3) clarification of procedures and guidance for compliance auditing and certification; and 4) making documents more "user friendly" by eliminating duplicate materials and discrepancies.
The process resulted in one new document being created, the Guidance for Use of the Cyanide Production Verification Protocol. The Guidance for Use of the Mining Operations Verification Protocol previously had been used as a surrogate to provide guidance for compliance of production facilities. This revisions process has also included consolidation of selected documents to reduce duplication and discrepancies and make materials easier to locate. Substantial revisions were made to 11 documents in this review and revisions process to improve clarity and for consistency both within and between documents. Information previously included in multiple documents were consolidated, where possible, into a single document. Documents used by operations in preparing for certification and used by auditors in evaluating compliance have been revised to account for ICMI's experience with Cyanide Code implementation, compliance issues, and evaluating audit reports over the past 14 years, as well as changes in industry practices since initial development of the Cyanide Code. ICMI released the revised program documentation in June 2021, and for purposes of audit compliance, the new program documentation was effective September 1, 2021.
Signatories and certification
The Cyanide Code is a resource for any gold or silver mine, cyanide producer or cyanide transporter regarding best practices for cyanide management. A company that becomes a signatory to the Cyanide Code commits to implement its Principles and Standards of Practice at its operations and to demonstrate compliance by having their facilities audited against the Cyanide Code's Verification Protocols.
The first 14 Cyanide Code signatory companies were announced in November 2005. Since then, the number of companies participating in the program has substantially increased. As of January 1, 2024, the Cyanide Code had 214 signatory companies, with operations in 48 countries. These include 57 gold mining companies, 32 cyanide producers, and 137 cyanide transporters.