World Mineral Production - NERC Open Research Archive - Natural ...

ZINC
Characteristics
Zinc is the 23 rd most abundant element in the Earth’s crust.
Zinc is a blue-grey metal; the freshly cut surface having a
typical metallic lustre, which quickly tarnishes to dull grey
when exposed to air, due to oxidation. It is moderately reactive
and burns with a bright bluish-green flame in air. It reacts with
both acids and alkalis. Malleable between 100°C to 210°C,
above 210°C zinc becomes brittle and can be powdered. Zinc
is non-magnetic.
Zinc does not occur in nature in the form of native (free)
metal. The most commonly found ore minerals are sphalerite
(zinc sulphide, ZnS), also known as zinc blende, and its
variety marmatite (zinc sulphide containing some iron
sulphide, (Zn,Fe)S), from which over 95 per cent of the
world’s zinc is produced. Other economically important zinc
minerals include smithsonite or zincspar (ZnCO3), willemite
(Zn2SiO 4) and hemimorphite (Zn 4Si 2O 7(OH).2H 2O), which
may occur in the near-surface weathered or oxidised zone of
an orebody. Less important are metamorphically-formed zinc
oxide ores such as the spinel, franklinite (Zn, Fe, Mn)(Fe,
Mn) 2O 4) or zincite (ZnO).
Zinc deposits are formed by deposition from hydrothermal
brines and are generally polymetallic, commonly including
economic levels of copper, lead, silver, cadmium, bismuth, tin
and gold. Economic levels of barite and fluorite may also be
present. Zinc ore deposits are widely spread throughout the
world and mining is currently carried out in more than 50
countries. China, Australia, USA, Canada, Kazakhstan and
Mexico have the largest zinc reserves (Cohen, 2007).
Before the zinc can be recovered from ore concentrate, the
sulphur content must be removed by sintering. The
concentrate is brought to a temperature of more than 900°C
converting the sulphide into the more active zinc oxide and
sulphur is driven off as sulphur dioxide gas which
subsequently is converted to sulphuric acid, an important
commercial by-product. The zinc can then be extracted from
the calcine either by leaching and subsequent electrolysis or
by smelting in a blast furnace. Today over 90 per cent of zinc
is produced in electrolytic plants. Smelting is extremely
energy intensive but has the advantage that it allows
simultaneous production of lead, commonly associated with
zinc in ore bodies. Electrolytic recovery produces >99.9 per
cent pure zinc requiring no subsequent refining (American
Zinc Association, 2008).
Total world reserves of zinc are 180 million tonnes of which
Australia holds 42 million tonnes, China 33 million tonnes and
Peru 18 million tonnes (USGS). At present, approximately 70
per cent of the zinc produced worldwide is primary and 30 per
cent is from recycled or secondary (including manufacturing
scrap) sources. The level of recycling is increasing and over
80 per cent of the zinc available for recycling is recycled
(International Zinc Association, 2008).
Uses
Current global uses of refined zinc (ILZSG, 2008):
• galvanizing (47%)
• brass and bronze (19%)
• zinc alloys (for die-casting industry etc.) (14%)
• chemicals (9%)
• semi-manufactures (8%)
From these first-use manufactures zinc is transformed into in a
broad range of products. The main application areas are in
construction (45 per cent), transport (25 per cent), consumer
goods and electrical appliances (23 per cent), and general
engineering (7 per cent). Zinc’s ability to protect iron from
corrosion in galvanising determines its most important use,
and most of this product goes to supply the construction
industry. Overall, about 75 per cent of zinc used is used as
metal. The remainder is used zinc compounds mainly by the
rubber, chemical, paint, and agricultural industries
(International Zinc Association, 2008).
World production in 2006
World zinc production (slab zinc) in 2006 was 10.8 million
tonnes. This was a six per cent increase on 2005. Production
increased steadily during the period 2002 to 2006, showing an
overall increase of 11 per cent, although with a slight dip (two
per cent) from 2004 to 2005. China remained the topproducing
country with 3.2 million tonnes in 2006. This
represents a 14 per cent increase on 2005 and a 45 per cent
increase since 2002. Canada was the second-largest producer
with 0.82 million tonnes and the Republic of Korea third, with
production of 0.67 million tonnes.
Prices
Throughout 2006 zinc was one of the best-performing metals
on the London Metals Exchange (LME), achieving a record
high of US$4580 per tonne on 9 November. The rapid price
rise began in July 2005, climbing to previous record highs set
during 1997 by the beginning of 2006 (see figure). This rapid
price increase was attributed to several factors: a 15-year low
in LME stocks of zinc, increased world demand, tightening
world supply, and investment buying. World mine and
refinery production both increased in 2006, driven primarily
by China and India. Excluding China, world refined zinc
consumption outpaced supply. After an initial decline in 2007,
the price staged three recoveries peaking at US$4120 per
tonne on 9 May, US$3820 per tonne on 24 July and finally
US$3161 per tonne on 15 October 2007. The high prices
achieved in 2006 resulted in the reopening and expansion of
zinc mines worldwide during 2007. This resulted in a supply
surplus with corresponding concerns and falling prices in the
second half of the year (Giglio, 2007).
This decline in zinc prices also corresponds to a period of
sharp decline in physical premiums 4 beginning in May 2007,
although this had stabilised across the USA, Europe, and
Japan over the last quarter of 2007 (analysis by Macquarie
Research, reported in International Mining online, January
2008). The fall in premiums is likely to have a significant
impact on both producers and traders; given the strong
increases in freight prices over the previous 12 months, which
saw many more than double,. In addition, physical metals
premiums tend to be strongly correlated with base metals
prices, giving a good indication of the physical availability of
a metal, correlating here with the dip in production for 2005.
The supply of zinc has been predicted by many to meet, if not
exceed, demand over the next few years with new zinc mines
being commissioned throughout 2007 and more planned for
2008. At the beginning of 2008 analysts from ABARE, the
Australian Government economic research agency, were
4 The physical metals premium is the price that metals purchasers are
required to pay (freight, insurance, warehousing and logistical costs
etc. in addition to the LME price) to receive delivery of their purchase
at a specified location.
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