extractive industries

The valuer is more likely be called upon to value extractive industries near population centres. For example, quarries to provide materials and 
various rock products to specification, largely for the construction industry. They may also involve an allied industry for example, sandstone cutting
and masonry which relies on the excavation of suitable sandstone.


The extraction of rock for use mainly in ready mixed concrete production, road base, foreshore protection and bituminous concrete. The materials
extracted must be clean, strong, durable and of a suitable shape, density, strength, porosity and permeability to meet the technical specifications and
standards set by the Standards Association of Australia, state road authorities and local councils. To achieve these standards and specifications,
equipment such as crushing and screening machines usually operate on site as part of the extractive industry.


Sand and gravel are extracted largely for use in the construction industry as constituents in the making of ready mixed concrete, concrete based products,
and bitumen. Soil is extracted mainly to supply material suitable for topdressing, garden uses and as fill material for landscaping.



Surface mining is usually undertaken where the mineral or substance to be mined occurs close to the land surface, allowing access to the mineral by
removing layers of soil and rock (overburden) which lie on top of the ore body or enclose it. Surface mining can consist of either "strip mining" or "open
pit mining":


Typically, the overburden is removed by cutting a trench or box cut to expose the mineral bearing zone. The overburden is usually stockpiled and should
be used as a screen to the mining operation and vegetated. When the ore from the box is removed the mine will advance following the ore body which
forms the floor of the workings.


Minerals such as iron and copper can often be mined using this method. It is similar to strip mining but where strip mining will usually only extract
one or two ore bodies which are located close together an open pit mine may extract a number of ore bodies at various depths.

A open pit mine will establish various levels or benches within the mine. The shape of the pit is determined by the dimensions of the ore body and
the need to maintain stable slopes within the pit. Mining usually commences where the ore bodies are closest to the surface. Strip and open pit mining
are the preferred methods where possible, as it is much cheaper than underground mining.


Mineral sands such as rutile, zircon and monazite bearing silica sands are usually found in coastal areas within sand dune systems. They are mined
as a surface mining operation using either wet or dry methods depending on the availability of water and the extent of the ore zone.


Underground mining is employed where ore bodies occur at depths which make surface mining uneconomic. Underground mining is generally
more expensive, requires greater technical skills, is more dangerous and labour intensive than surface mining. Entry to an underground mine is by
way of shafts or drifts (sloping tunnels) providing access for workers and equipment. Most mines utilise expensive and extensive support systems as
the surrounding rock or the ore body is usually not strong enough to support the excavation.


Offshore mining can include the mining of marine aggregate and mineral sands from offshore coastal waters. The conventional method of operation is
to dredge material from the seabed and load it into a ship where an initial separation may be undertaken to remove part of the bulk residue material.


Economic minerals can occur in various proportions in the ore body for example, haematite as mined may contain up to 70% iron but rock containing
only minute particles of gold (for example, 99.9% of barren rock or waste material) can be economically mined. Usually the bulk of the material mined
is transported to the surface where some form of processing takes place to separate the mineral from the waste product. In some cases the primary
processing is carried out underground where large fragments of ore are crushed to a finer size prior to transportation to the surface.


The environmental impact issues are particularly important to the economics of a new mine/quarry or the expansion of an existing mine/quarry.
The Environmental Impact Statement (EIS) must address all matters specified as well as those matters generally specified in the relevant acts and
regulations. For example, Clause 34 of the Environmental Planning and Assessment Regulation 1980 (NSW).

The factors to be considered include a description of the proposed development, the existing environment, the impact of the proposed development on
the existing environment and an assessment of that impact taking into account proposed environmental safeguards. If the environmental protection
safeguards cannot be met or are too expensive, the proposal cannot go ahead and the "highest and best use" will be the next best option. The valuer
should consider whether or not mining/quarrying is compatible with surrounding development. Factors which should be considered in the valuation
report are:

Other factors to be addressed when assessing an existing or potential mine or quarry are: