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Aggregate

The sand, gravel and rock used for building and road making are called aggregate. They are the most widely used mineral products in the New Zealand, and the most valuable. More than six tonnes are used each year for every person in New Zealand. Aggregates on the West Coast are mostly extracted from river deposits and alluvial terrace deposits. Sand, gravel and rock extraction operations are sited locally because of the high cost of transport.



above and below: Aggregates on the West Coast are mostly extracted from river and alluvial terrace deposits.

Washouts and high flood levels on West Coast rivers create a continual demand for riprap for river and coastal protection work. Natural, large river boulders and large quarried blocks of granite, limestone, and lesser amounts of sandstone and schist are extracted from quarries and pits. In order to keep cartage costs to a minimum, a network of quarries is spaced along the main roads.

Selected aggregates and decorative stone are shipped by barge from Greymouth and railed to distribution points in the North Island.


The main uses of aggregate are:

  • base course material used as foundation for sealed and unsealed roads
  • repairing and surfacing roads
  • maintaining railways
  • manufacturing concrete products such as blocks, pipes and paving
  • making bitumen paving
  • drainage and filtration
  • making concrete (concrete consists mainly of aggregate)

Aggregate production, quite literally, forms the foundation of any region's infrastructure and future development.

West Coast Aggregate



above: Beaches are a source of West Coast aggregate.

below: A typical river operation.


below right: Locally sourced aggregates were used in the construction of the new Grey River rail bridge that has streamlined transport of West Coast coal to Lyttelton.

below: Aggregates are used as the foundation for the regions roads.
Quantity & value of West Coast aggregate production
Aggregate production, quite literally, forms the foundation of any region's infrastructure and future development
Commodity 2002 Quantity
tonnes		 2002 value
$NZ
Building and dimension stone
2,550
55,500
Decorative pebbles including scoria
13,100
94,550
Limestone and marl for cement
750,000
2,842,500
Limestone for agriculture
87,300
1,300,100
Limestone for industry
100
1,000
Pounamu
350
441,150
Rock for reclamation & protection
67,500
431,700
Rock, sand and gravel for building
27,350
214,200
Rock, sand and gravel for roading
194,650
1,652,200
Rock, sand, gravel and clay for fill
10,150
30,550
Sand for industry
4,700
37,950
Talc
10
4,000
TOTAL
1,157,760
7,106,400