ICMI Seeks Comments on Proposed Requirement for the Use of Colorant Dyes in High Strength Cyanide Solutions at Mining Operations

The International Cyanide Management Institute (ICMI) announced today that it is seeking stakeholder comment on a proposed change to the International Cyanide Management Code program that would require mining operations to use colorant dyes as an aid in visually identifying cyanide releases.


The chemical manufacturing industry has historically added colorants, odoriferants and other indicators to dangerous chemicals that do not possess an obvious identifying characteristic. The purpose of these indicators is to provide a quick and distinctive identifier to an otherwise indistinguishable chemical; such as natural gas, butane and propane, and in certain sensitive ecological areas, diesel and fuel. Colors are used to highlight dangerous liquids where the addition of the dye does not impact the chemical process.

Although the Cyanide Code requires many measures to manage and control cyanide solutions, including piping and tank labeling, there are none to clearly identify high concentration cyanide outside of proper containment.

To provide for such identification, some gold mining companies and operations introduce colorant into reagent-grade cyanide solutions.  This use of dyed cyanide has occurred since at least the early 1990’s.  Companies and mining operations have provided a number of rationales for using colorant dyes in reagent-grade cyanide solutions.  These include:

  • Providing a visual marker that readily identifies reagent-grade cyanide solutions.
  • An identifier of reagent-grade cyanide solutions that are in contact with workers.
  •  Visual indicator to medical responders, assisting in cyanide exposure identification and decontamination.
  • An indicator that hydrogen cyanide gas could be present in areas usually not at risk.
  • An indicator of the loss of primary and secondary containments, such as leaks around pump seals, flanges and spillages.
  • Early warning prior to a major failure.
  • Visual clean-up marker for releases.
  • Identification of equipment potentially needing decontamination.
  • An indicator of reagent-grade cyanide salts through a reddish pink tint, identifying them from other salts that may be present.

It is reported that the dye predominately used to color cyanide solutions is the synthetic red food dye Carmoisine.  Although Carmoisine and Red No. 40 have been scrutinized as food additives, and Carmoisine has been banned in several countries for use in the food industry, these dyes remain available for non-food related uses.  There are unconfirmed reports that blue dye is also being used as a cyanide colorant.

Colorant dyes are manufactured in several forms and packaging options, including dry powders and granules, liquids, and concentrates.  Most facilities introduce the dye as a dry powder or concentrated solution that is added to the cyanide mix-tank, using a standard concentration of dye to liquid solution of 0.03 g dye/L solution @ 23% NaCN concentration.

Carmoisine and Red Dye No. 40 can be purchased as an industrial dye, and both are classified as non-toxic.  When working with the dye in a powdered form there are recommended safe-handling requirements.  ICMI’s preliminary investigation suggests that the cost of using dyed cyanide is insignificant and that currently available dyes do not interfere with metallurgical processes, cyanide analyses or operation of cyanide treatment or destruction facilities.  Mining operations having operational experience using dyes have informed ICMI that tailings solution have not exhibited coloration as a result of the dyes.

While the total number and locations of jurisdictions in which dyed cyanide is currently used is unknown, it is known that dyes are being used in gold mine operations in Mexico, Canada, Guatemala, Argentina, Ghana, Australia and Papua New Guinea. Comments and discussion to-date have not identified any jurisdictional restrictions on use of dyes to cyanide.

At many operations multiple water streams, water holding facilities, and water sources are present. Many of these do not contain cyanide, such as wash water, standing rainwater at open facilities, and freshwater for dilution and reagent mixing.  At these facilities, clear identification of reagent-strength cyanide through dyes, and identification of other standing water contaminated by reagent-strength cyanide, would likely aid in response by allowing certainty and quick identification of high strength cyanide solution.

ICMI is informed by current dye users that dyes are low-cost in the quantities used.  To achieve the desired color using a target concentration of 111 grams dye/metric ton of cyanide on a dry basis, the current cost of Red Dye #40 powder from one cyanide supplier is reported to be approximately US$2.40 per metric ton of cyanide, without dye packaging.


The incorporation of dye to reagent-strength cyanide as a requirement of the Cyanide Code offers an opportunity to enhance protection of personnel and the environment.  Addition of colorant to reagent-grade cyanide is a proven indicator that has been adopted by a number of companies and operations (both signatory and non-signatory) as a best practice.  Use of dye by these companies is believed to enhance product awareness, personnel safety, and to provide a quick indication of cyanide leaks and spillages.

ICMI proposes to require that reagent-strength cyanide solutions be clearly identified at mining operations through use of colorant dye.  This requirement would be added through addition of appropriate language to the Cyanide Code’s Implementation Guidance, ICMI’s Mining Operations Verification Protocol, the Auditor Guidance for Use of the Mining Operations Verification Protocol, and other supporting documentation.

ICMI envisions that this proposed change would become effective July 1, 2019, allowing for companies to make changes to procedures, documentation, to train workers and emergency responders about recognition of dyed cyanide solutions, and for changes to procurement contracts with chemical suppliers. 

ICMI needs greater information from its stakeholders before a decision can be made about dyes in high-strength cyanide solution, particularly from mining companies.  Stakeholders are invited to comment on this proposed requirement for mining operations, including its advisability, any policy or technical issues it raises, as well as any other related issues that ICMI should consider about this proposed change to the program. Stakeholders wishing to comment are requested to provide written comments to ICMI President Paul Bateman at pbateman@cyanidecode.org by no later than October 9, 2017. ICMI will announce its final action on the proposed Cyanide Code expansion after its Board of Directors has considered stakeholder comments.

Wednesday, August 9, 2017