Why Quarrying?
This section has been developed to provide you, the visitor, with an overview of
quarrying and its importance to New Zealand’s economy and overall growth.
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Part 1 – An introduction to quarrying
Part 2 – Mineral wealth in New Zealand
Part 3 – Extraction processes
Part 4 – Issues facing our industry
Part 5 - Statistics
1 An Introduction to quarrying
Fact – New Zealand uses 8 tonnes of aggregate per person per year in construction
Stone is the most widely used construction material in the world. Its use goes back to the
dawn of civilisation. When some 4,000 years ago men cut stone to build the well known
structures of the Cheops Pyramid in ancient Egypt and the historical site at Stonehenge in
Great Britain, quarrying activities were already well established in many areas of the
world. The Great Wall of China, constructed over 2,000 years ago, consumed staggering
quantities of stone that was provided by the quarry industry in that region.
The demand for quarried aggregates is enormous. Quarries underpin the ongoing
development and maintenance of our country. Stone is an essential component used in the
construction of homes, factories, schools, hospitals and shopping centres. Road, railways,
airport and port construction consumes large volumes of aggregates in every form, as
does the ongoing forestry and rural development. Conservation initiatives are supported
by the use of stone to protect landforms.
The quarry industry produces many millions of tonnes annually for use by the home
building industry. Depending on design and site condition, over 4,000 tonnes of
aggregates are used in the construction of just one kilometre of standard highway
pavement, while the building of a new six lane motorway can consume in excess of
20,000 tonnes for the same distance.
Thus the quarrying and aggregate production industry plays a vital role in the nation's
economy, not only by providing essential materials but in also by providing employment
opportunities which are in many cases in rural areas.
2. Mineral Wealth In New Zealand
The earth abounds in the deposits of different minerals. Included in our wealth is stone
and rock for aggregates, limestone deposits which are used in the manufacture of
fertilisers, cement and for road surface rehabilitation, and a range of clays for brick,
ceramics and pottery products.
Aggregates are obtained from the extraction and processing of rock or stone from two
main sources. These are Quarries and Riverbeds.
Quarries
The first source is a quarry where rock is obtained by blasting a quarry face, then
crushing and screening material to produce a wide range of aggregates in various sizes
and to specified quality limits. There are three basic types of rock used to produce most
quarried rock aggregates.
1) Igneous: rock which formed as a result of volcanic activity and then solidified from the
molten lava flow. Examples are basalt and andesite rock.
2) Sedimentary: rock which formed in the distant past by the settlement fine sand and grit
under pressure on a seabed. Greywacke and limestone deposits are most common.
3) Metamorphic: rock e.g. quartz are formed by the action of heat and or pressure on
existing rock formations.
Riverbeds
Gravels and sand, the second major source of aggregates are formed by the past natural
erosion of existing rock and then transported by ice or water to be deposited in old or
existing riverbeds or into the sea. These deposits normally consist of rounded, separate
particles and are more easily extracted than the quarried material. The smaller sized
stone, i.e. minus 25mm is usually sold in an uncrushed, washed state for use in concrete
production. The larger sizes and boulders can be crushed and processed into nominated
product specifications.
New Zealand can be roughly divided into two when looking at the quarrying and
aggregate production industries. In the North Island the main source of aggregate
production has swung away from the rapidly depleting alluvial riverbed gravel deposits
and over to the hard rock quarries or land based gravel reserves.
At this time the community demand for aggregates in the South Island can still in the
main be met by extracting river gravels. However in some areas the availability of river
gravels is quickly diminishing and some hard rock quarries are being established to meet
demand.
Soil, clay or other soft or weathered materials which normally overlay quarry resources
and land based gravel deposits is termed overburden. If the depth of overburden is too
great then it may be uneconomic to attempt the extraction of rock or gravel at a specific
site.
3 Extraction & Processing
In the past hard rock quarrying was undertaken by the use of manual labour. The
tasks were hard, backbreaking and often dangerous for the labour force.
Today the two main sources of aggregates are extracted in different ways. Quarried rock
is now normally broken out from the main faces by means of controlled blasting. Each
blast is well planned to provide a measured quantity of loose rock whilst minimising
ground vibration and noise within the immediate surrounding area. Blasting usually
occurs at preset times and where necessary a system of prior warning for neighbours is
put in place.
Gravel and sand excavated from dry pits or river beds generally do not require blasting to
loosen the resource. Hydraulic excavators and Front End Loaders are normally used for
this task. A wide variety of mechanical loaders are employed within the industry to load
the blasted rock or excavated gravels on to waiting dump trucks, in preparation for
haulage to the crushing, screening and washing plants.
At the processing plant an array of jaw, gyratory and impact crushers followed by various
washing systems and screening units transform the raw material into a range of quarry
products. These products vary from very tightly specified crushed or uncrushed screened
and graded rock and stone for use in highway construction, to a selection of lower quality
material, which is used for general non-specified roading works.
Often the higher quality products are combined with other materials such as cement to
manufacture concrete or bitumen to produce asphalt pavement surfacing.
Issues facing our Industry
One of the fundamental issues facing the Quarrying industry is the fact that, even though
demand for quarry products continues to grow at an ever-increasing rate, in many District
and Regional Plans, quarries themselves are not recognised as an essential resource that
needs to be provided for. Urban developments such as subdivisions require vast amounts
of aggregate, yet they are the very things that tend to take precedence over quarries when
determining land use.
A consequence of this urban development is that of increasing compliance regulations
imposed on quarries, due to these developments getting ever closer to the existing quarry
operations, i.e. the encroachment of urban sprawl limiting the production of essential
rock. Many quarries are in fact feeling the effects of reverse sensitivities as they are
afforded little or no protection from planning authorities.
In some rapidly developing areas if there are insufficient approvals granted for adjacent
new quarry and pit operations there might be a shortfall in the supply of aggregates to
that locality. The outcome of this will be the need to haul aggregates by heavy trucks
over much greater distances, which will result in increased cost to deliver quarry
products, and has the potential to cause greater adverse environmental effects and road
safety impacts.
It is important that regional authorities start to recognise the importance of local quarries,
and ensure that not only existing sites be given more consideration, but also that potential
quarry sites also be factored in to any development plans to cater for future needs.
Quarrying operations can be well managed and any adverse, or perceived adverse effects
can be mitigated by the development and implementation of a Quarry Management Plan
to ensure the activity is operated to a good standard and complies with the conditions
imposed on the site.
Good communications and consultation assist greatly in improving community relations
for all parties involved.
5 Statistics
Here are a few facts and figures to indicate show the importance of quarrying within New
Zealand.
 The Te Papa museum, in Wellington, used over 80,000 cubic metres
of concrete in its construction, using aggregate sourced from local
quarries.
 The value of New Zealands coal and mineral production is in excess
of $1,000,000,000 per year excluding petroleum & water.
 The number of people employed through the industry, either directly
or indirectly, exceeds 25,000.
 The quarry and aggregate industry in New Zealand currently
produces in excess of 25 million tonnes of processed product annually
with an estimated value of $450 million.
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