2017 Report: Mineral Exploration Australia

Mineral exploration is the process of gathering information to assess the mineral potential of a given area by determining geologic anomalies that may lead to mineral discovery.

Drilling programs are then undertaken to provide estimates of the extent and quality of the deposit. The immediate product of exploration is the identification and geological knowledge of a defined area which may be economically feasible to extract later on.


The stages of mineral exploration

The early stages that a mineral exploration includes are:

  • Gathering and analysing publicly available information on potential areas to identify areas of interest and to plan the following stages.
  • Once geologically favourable areas worthy of further exploration are identified, the explorer would apply to secure the mineral rights. On Crown land in Western Australia, this is determined by many factors including ongoing native title claims by indigenous Australians through the Native Title Act.
  • Reconnaissance activities to identify the presence of mineralisation and define targets for further exploration which can include:
    • Prospecting and geological mapping
    • Rock sampling
    • Geophysical & Geochemical surveys

Once anomalies have been identified, exploration can move to advanced exploration activities to determine if there are deposits. Advanced exploration activities can include:

  • Trenching: Removing the shallow overburden and then blasting a trench in the rock to gather more material for sampling.
  • Drilling: Reverse Circulation Drilling produces rock chip samples that can be examined to determine the mineral concentration and depths at which mineralisation occurs.
  • Sampling: The collection and testing of a representative part of the mineral deposit.
  • Feasibility: A study on developing a mine can be conducted to estimate the costs of a mine, expected revenue, mine life, and environmental rehabilitation costs.

Mineral exploration outlook


mineral exploration drill with workers

The graph below shows the trend in mineral exploration expenditure in Australia. Western Australia was the largest contributor to the rise this June quarter 2017 (up 6.5%, $17.4m).

Across Australia exploration on areas of new deposits increased 32.1% ($33.0m) and expenditure on areas of existing deposits rose 31.6% ($74.1m).

Mineral Exploration Expenditures in Australia, 2009-2017.

Mineral Exploration Expenditures in Australia

Source: ABS – 8412.0 – Mineral and Petroleum Exploration, Australia, Jun 2017

Mineral commodity prices are a key determinant of the level of exploration activity in Western Australia. The discovery of large deposits encourages further exploration by all exploration firms attracted by the potential value of the land surrounding the original discovery.

Western Australia also makes up one-third of Australia’s land area, creating significant opportunities for those willing to explore.


Minerals in Western Australia and beyond

Exploration for gold has attracted the most money in Western Australia, followed by iron ore. The country itself is the world’s leading producer of bauxite, ilmenite, rutile, and zircon and the second largest producer of gold, lead, lithium, manganese ore, and zinc.


Encouraging mineral exploration in Australia

Australia’s mineral resources are an important component of the nation’s wealth and have a comparative advantage in the production of mineral commodities which stems from

  • A rich and diverse mineral endowment
  • High-quality regional-scale geoscience information
  • Advanced exploration, mining, and processing technologies
  • A skilled workforce
  • Low population density

These factors mean that modern mining can be undertaken in line with lowered risk levels and increasing economic and environmental performance.

Paperless systems

Castle Drilling have been utilising cloud-based storage for all systems for some time.

This has enabled us to keep up to date client and employee access at all times. While in the field, each drilling crew have a robust iPad which has an integrated daily drill reporting system that is trailered for CDC requirements.

Take 5s, rig inductions, site inspection checklist and pre-start forms are also available through the application. All forms are automatically forwarded via email to nominated email addresses upon completion and approval. Employee forms such as timesheets and leave forms are quickly emailed to administration staff. The system ensures positive and effective communications between the office and the field.

Also, the entire safety management system is available in digital format including SDS and SWP as well as maintenance records and schedules. Operation and part manuals of the plant can be accessed quickly and easily by drill crews, and efficient use of order forms and stocktakes gives a heightened level of support to operations.

An Introduction to Reverse Circulation Drilling

When choosing a drilling method, especially for exploration and grade control, one must consider many factors such as cost, time, environmental impact, depth of drilling and sample quality. Reverse Circulation drilling offers many advantages over other drilling methods, such as Rotary Air Blast drilling or diamond drilling. This article will explain what Reverse Circulation drilling is, its benefits, its health and safety considerations, and why it is the best method of grade control.

1. What is Reverse Circulation drilling?

Reverse Circulation drilling, or RC drilling, is a method of drilling which uses dual wall drill rods that consist of an outer drill rod with an inner tube. These hollow inner tubes allow the drill cuttings to be transported back to the surface in a continuous, steady flow.

rc drilling

Unlike diamond drilling, it compiles sample rock cuttings instead of rock core. The drilling mechanism is most often a pneumatic reciprocating piston called a hammer, which in turn is driving a tungsten-steel drill bit, specifically made to be able to crush hard rock.

The hammer is used to remove rock samples which are pushed through the machine with compressed air. When air is blown down the annulus (ring-shaped structure) of the rod, the pressure shift creates a reverse circulation, bringing the cuttings up the inner tube. When the cuttings reach a deflector box at the top of the rig, the matter is moved through a hose attached to the top of the cyclone.

The drill cuttings will travel around the cyclone until they fall through the bottom opening into a sample bag. These bags are marked with the location and depth of the place where the sample was collected and can be transported directly to the assay lab for analysis.

2. The benefits of RC drilling

Reliable and uncontaminated samples:

When the cutting travels through the bit into the inner tube towards the cyclone, it is not introduced to other areas of the hole, keeping it free of cross-contamination. This creates the possibility of producing large quantities of high quality, reliable samples.

Sample cuttings are easier to catalogue and keep track of. Because the samples collected will have an exact location and depth at which they were found, surveyors and interested parties will be able to locate mineral deposits more precisely.

High drilling penetration rates:

RC penetration rates are comparable to open drilling methods and are often faster at greater depths. Sample velocity through the inner tube can reach speeds of 250 m/sec, making the retrieval of drill cuttings a rapid but safe method requiring fewer man-hours.

Production rates are superior to diamond drilling; rates of 200-300 m/day are routine at speeds faster than 10 m/h. Therefore, results from RC drilling can be revealed to clients much faster because the drilling process takes less time.

Versatile in tough conditions:

RC drilling is fairly straightforward and requires far less water than diamond drilling, making it ideal in places such as Australia, where water may be scarce or costly. RC drilling is also a more cost-effective method than diamond drilling, with operating costs reduced by up to 40% compared to diamond drilling.

Cost reduction is especially noticeable in geologically challenging locations, which would increase the cost of more conventional drilling methods even more. RC drilling will keep those costs down since it is more resilient in harsh environments.

3. Why is RC drilling best for grade control?

Grade control is used to define the ore grades and blocks in the pit. For an exploration program, the quality of the samples is imperative for mine planning and blasting—the samples must be reliably accurate.

RC drilling is the superior method used for grade control in open pit mining operations because:

  • samples obtained via RC drilling are free of contaminants
  • the samples are collected at the drill and sent directly to the lab to be assessed
  • RC sampling requires less handling than other methods
  • less handling results in cost reduction and faster turnaround times

The reliability of the cuttings produced during RC drilling  is an industry asset. RC grade control is the most cost effective and efficient method to differentiate between waste rock and minerals.

4. Key safety and environmental considerations

Exploration drilling is strictly controlled and regulated when an exploration licence is approved. Most drilling requires further governmental approval, which will demand a thorough environmental survey, proposed methodology, administrative plan, and environmental mitigation.

RC drilling safety regulations will vary depending on location, but there are general precautions to observe. RC drilling has some inherent risks to be aware of.

The sounds of constant hammering of drill bits into rock combined with the use of loud air compressors may cause hearing loss. That’s why occupational health and safety laws require workers to wear some sort of hearing loss protection as well as all other appropriate personal protective equipment. This includes not only ear plugs or ear muffs but also respiratory masks, safety footwear, hard hats and industrial work gloves.

RC drilling requires ‘Samplers’ or ‘Offsiders’ to process the cutting samples from the cyclone. They may have to manually handle some of the downhole equipment, putting them in a more hazardous situation than in a standard drilling site such as well drilling. They must remain vigilant about a number of hazards such as:

  • the physical strain they could receive from manually handling samples,
  • the potential of falling objects,
  • proximity to compressed air, and
  • pinch points or areas around the rig that could be the source of crush injuries.

However, adopted control measures make it more difficult to access potential pinch points, and added interlocks prohibit operation under unsafe conditions.

Because RC drilling has a small rig footprint, it eliminates the need for extensive earthworks. This means RC drilling has a minimal environmental impact.

5. RC drilling best practices

There are many procedures and techniques required to achieve the best possible results from RC drilling. Holes are set up similarly to conventional holes, and the most important element of RC drilling is the sample. The goal is to capture as much sample as possible from the hole, preferably through the inner tube.

High inside sample circulation is achieved by having the appropriate clearance between the bit shroud and the hole wall. This should forge a seal, thereby forcing the sample inside. If there is water in the hole, allow the hole to collar off as this helps to keep the samples dry, making them easier to transport and process.


Since its inception in the early 1970s in Australia, RC drilling has become a preferred method for initial exploration and grade control due to its many advantages:

  • the samples extracted by RC drilling are reliable and free of contaminants,
  • the method is timely and cost-efficient,
  • it is well-suited for difficult terrains,
  • it has high penetration rates, and
  • it has minimal environmental impact.

Taken together, these positive aspects of RC drilling make it an excellent choice for mining exploration and grade control.

What is Reverse Circulation (RC) Drilling? [Inc. Video]

Reverse circulation (or RC as it’s more commonly known) drilling is an essential tool in the mining industry. In addition to other oil rigs and drill rigs, reverse circulation drills assist in the productivity and accuracy in mining jobs.

RC drilling is a drilling method involving a large rotary drill and air compressor that yields high quality mineral and rock samples, free from contamination and material interference.

It is the preferred method of mineral exploration, drilling and in-pit grade control because it is fast and cost-effective.

What is RC Drilling?

Much like air core drilling, RC drilling returns cutting to the surface through an inner tube inside the rod. This is achieved by blowing air down the rods at a rate up to 1500 Pascals. This creates a pressure differential that pushes cuttings and water up via air lift.

The drilling component is powered by a pneumatic reciprocating piston (also known as the hammer), which drives a steel drill bit.

The two most commonly used drilling bits in RC systems are the fixed cutter and roller cone, both of which are advantageous depending on the project and geographical location of the site.

RC drilling is primarily used on large machinery and drill rigs and often goes to depths of 500 metres. [Source]

High quality RC equipment also has the ability to dry out the rock with large air compressors before the drill hits, which provides dry rock chips and, in turn, better samples.

History of Reverse Circulation Drilling

Grade control rig

The innovation behind RC drilling is proudly Western Australian.  During the middle of the last century, drilling in soft iron ore and mineral sands using the traditional open hole techniques was proving to be difficult. Due to this need, Bruce Metzke and John Humphries of Kalgoorlie created the first RC drill rods in 1972 [source].

As the years pass, the need for cleaner samples increased, which led to the development of the RC hammer in 1990. Around the same time, high pressure boosters and auxiliary were added to penetrate faster and to create deeper holes.

The introduction of this technology made RC drilling the most cost effective and accurate method available, particularly in an era where mining costs were rising.


In Western Australia, reverse circulation drilling is the predominant technique based on a number of advantages.

  • A higher percentage of uncontaminated cuttings
  • Drilling rate similar to open hole drilling, but can often be faster and penetrate greater depths
  • One of the most accurate drilling methods
  • Quick retrieval of sample rates
  • Dry samples allow for easier analysis

Reverse circulation drilling has earned a reputation for good results in the mining industry because of its ability to attain high quality samples and its cost effectiveness.  If you are after RC drilling machinery for your next project, please contact us for further assistance.

RC Drillers achieve 0.3% sample errors from a 9000 sample population


CDC achieves record low drilling campaign sample error percentage.

During a recent Reverse Circulation exploration drilling campaign, Castle Drilling Company delivered the client 100% sample return (2x 20kg samples with nosample loss at all), and 28 errors over a sample population of 9000. These errors largely consisted of spilt bags and numbering issues which were easily rectified.

The challenge during the 6 week program was to provide the client with innovative solutions to the non-typical requirements they had, with the entire crew understanding how imperative sample quality is to the clients bottom line. 0.3% still allows room for improvement however!

This article was recently published on LinkedIn.

What is grade control and how can it save you time?

Traditionally, a geologist oversees grade control in the mining industry. However, over the past two decades, we have seen an emergence of technology that assists with this procedure. Today will take a closer look at grade control and how it can improve the mining industry.

What is Grade Control?

Grade control is an essential part of the mining process because the metal being extracted from the ground is never constant.he first grade control machines to have guidance systems were introduced in the late 1990s. Since then, this technology has become more prominent – many manufacturers of earthmoving equipment now offer guidance systems that control blades and other machine parts using GPS technology.

How does it work?

Drilling machinery provides the operator with real-time grade guidance while they are drilling. What this means is that they are given information about the desired depth, slope and alignments (which was traditionally given to them by a specialist inspecting the site). Drilling samples are sent to laboratories for geologists to access the grade.

Why use it?

Controlling the grade is important for two reasons:


The grade of the mineral can vary dramatically due to depth. Geologists will use this information to define the economic limits, to ensure there is return on investment when mining the mineral.

At one point in an operation, mining becomes unprofitable because the grade of the metal is too low – the value of the metal in the ore is less than what it costs to mine it. Grade control stops businesses from running at a loss.


The milling process is designed to be as efficient as possible by being performed at a specific grade. When mining in a high-grade zone, it is possible for some of the metal to be lost unless it is blended with low grade metal.


Grade control technology improves efficiency, increasing the productivity and profitability of an operation. Grade control systems allow machinery to operate at a continuous pace, rather than having to stop for a grade checker to come and measure the excavation, as with conventional equipment  – a process that often needs reworking. It also decreases the need to do prep work and to check the grade after the deck. The overall benefit is that it will save you time (and thus money), without compromising on accuracy.


We hope the information provided has given you an insight into grade control and its benefits. If you require a drill with grade control for your project, please contact us as we may be able to assist you.