Page Index
Introduction  
History of Zinc  
Uses of Zinc  
Zinc Pricing  
Lead and Zinc Geology and Exploration

Introduction

The base metal zinc (symbol Zn) is a lustrous (light-reflective) bluish-white metal, ordinarily brittle and crystalline. Zinc becomes malleable and ductile when heated to between 110 and 150? Celsius.

Although not abundant in nature, zinc has several key commercial applications. It is primarily used as a protective coating material in transportation, construction, and electrical equipment. Zinc is also an essential animal nutrient.

Zinc is most readily found in the ores sphalerite, zincite, calamine, and smithsonite, and is often mined in conjunction with lead, silver, copper, and cadmium.

The world's biggest zinc producers are Canada, China, Australia, Peru, Mexico, Ireland, and the United States.

For further information on zinc, visit the International Zinc Association.

History of Zinc

Zinc has been in use since ancient times. An alloy containing 87 percent zinc was discovered in prehistoric ruins in Transylvania; bronze objects containing zinc, discovered in the Middle East, are estimated to be 3,000 years old.

The Babylonians smelted copper alloys containing tin and zinc in the third century BC. Zinc was used to make mirrors and coins in China around 600 AD. Both the Greek and Roman civilizations actively used zinc to produce brass. Metallic zinc was produced in 13th-century India by reducing the calamine ore with organic substances like wool.

As explorers forged early trade routes, zinc's applications became well known throughout Europe and the New World. Zinc enjoyed a revival upon discovery in Europe in 1746 by Andreas Sigismund Marggraf.

Uses of Zinc

Zinc has many personal and industrial uses.

Human bones, teeth, and the immune and reproductive systems all require the fortifying power of zinc - the recommended daily zinc intake is between nine and 15 mg, and is derived from beef, liver, cheese, eggs, milk, and yoghurt.

Zinc is found in insulin, a treatment for diabetes, while creams and lotions made with zinc oxide are used to treat wounds, infections, and various skin disorders. Zinc is also found in sunblocks.

Zinc is essential in the preparation of alloys like brass and German silver; and it is sometimes utilized in making bronze. The metal is used for the negative plates in certain electric batteries, and in roofing and gutters in building construction.

Zinc castings turn up in everything from electronic devices to children's toys. Modern cars contain about 40 pounds of zinc each, much of it found in steel body panels. In addition to zinc oxide, other important zinc compounds include zinc chloride, used in adhesives and cements and to preserve wood, and zinc sulfide, which is used to make television screens and X-ray apparatus.

Zinc Pricing

Zinc is traded daily on the London Metal Exchange. The price is set each day at two separate sessions. First session: 12:10 p.m. and 12:50 p.m. Second session: 3:25 p.m. and 4:05 p.m.

Lead and Zinc Geology and Exploration

Because the base metals lead and zinc are most often found together in mineral deposits, that is how this section will consider them.

Principal lead-zinc deposit types include carbonate-hosted Mississippi Valley (MV) ores, sandstone-hosted ores, shale-hosted (or SEDEX) deposits, and volcanogenic (VMS) deposits.

Of sedimentary ores, the MV deposits have provided considerable past production of lead and zinc mined throughout the world. These deposits occur along the edges of large sedimentary basins in all parts of the world, are typically hosted by carbonate (dolostone) rocks, and form very large ore districts with numerous individual deposits within these camps. The former Pine Point district, NWT and the Viburum lead-zinc ore trend in Missouri are two notable examples. Data for individual deposits is highly variable, but an approximate range for MV deposits is from five to ten percent combined lead-zinc and one to 10 million tons. As with other zinc-lead deposits, sphalerite and galena are the main ore minerals.

Canada's north serves as a good example of carbonate-hosted ores. Here a total of 300 million tons have been mined from the Pine Point deposits, Polaris and Nanisvik. Together, these mines average two percent lead and 6.9 percent zinc. Recent exploration successes for carbonate lead-zinc deposits include Platinova's (1993) discovery in NE Greenland of a 55 million ton deposit grading 12 percent zinc and one percent lead, and Rhonda Mining Corp.'s (1996) discovery of the Esker deposit in the NWT, Coronation Gulf area. High-grade lenses of up to 8.6 percent zinc and 2.3 percent lead occur within a lower-grade geological resource estimated to be approximately 100 million tons.

For the shale-hosted (SEDEX) type of lead-zinc ore, examples in Canada include the giant Sullivan Mine in British Columbia and the deposits of the Yukon's Anvil district. In Australia, Mount Isa and the metamorphosed Broken Hill deposit are important economic examples belonging to this class.

SEDEX deposits consist of layers of massive sulfide interbedded with layers of sedimentary rock (shales, mudstones, and argillites). The massive sulfides are composed of alternating layers of iron sulfide (pyrite or pyrrhotite), with lesser amounts of sphalerite, galena, and layers of clastic sediments. The calculated average size and grade of SEDEX deposits is in the order of 45 million tons grading 6.8 percent zinc, 3.5 per cent lead, and 1.45 ounces/ton silver. Deposit size, however, can be quite large - up to several hundred million tons with grades up to 18 percent zinc and nine percent lead. SEDEX deposits are, therefore, important exploration targets, in spite of the fact that they are relatively rare and have metallurgical recovery problems due to the fine-grained nature of the sulfides.

Volcanogenic massive sulfide deposits (VMS) comprise the third significant category for world production of lead and zinc concentrates. This class of mineral deposit differs from the above by being associated with rhyolitic to basaltic flows and fragmental volcanics. The sulfides occur as more or less stratabound lenses with an underlying, commonly discordant zone of disseminated sulfides (stockwork or stringer zones) in highly altered rocks. The ores are polymetallic and of two major types: copper-zinc or zinc-lead (minor copper). Precious metals, along with tin, cadmium, bismuth, and selenium, can be recoverable byproducts with the base metals.

Examples of the lead-zinc type include the Brunswick Mine, New Brunswick, and the ores from the Buchans Camp, Newfoundland, while Kidd Creek Mine in Ontario and the numerous deposits in the Noranda camp typify the copper-zinc-type. While a few deposits are huge (greater than 100 million tons), 80 percent of VMS deposits fall in the range of one to 10 million tons. In the Bathurst camp (lead-zinc type) the average grade and tonnage of 29 deposits is 5.43 percent zinc, 2.17 percent lead, 0.56 percent copper, and 1.74 ounces per ton silver. For the copper-zinc type, the average grade and tonnage of 52 deposits in the Abitibi belt is 10 million tons grading 1.47 percent copper, 3.43 percent zinc, 0.07 percent lead, and about one ounce per ton silver. By the mid-1980s, over 1,000 VMS deposits had been discovered and the search for this economically important source of metals continues unabated.

Sandstone-hosted lead-zinc deposits are much less common. Well-known examples include the Laisvall, Vassbo, and Dorotea deposits in Sweden, Largentiere in France, and Maubach-Mechernich in Germany. In Canada, the Yava mine in Nova Scotia was mined for a short period in the 1980s. Deposits of this type have ranged in size from very small prospects to 225 million tons. These deposits are lead-rich (2-5 percent) and generally contain insignificantly amounts of zinc (0.2-0.8 percent). The deposits are only of local significance (e.g. in Sweden) and exploration is virtually non-existent.