Clitheroe
Shap
Horwich, Bolton
Chorley
Horwich, Bolton
Clitheroe
Shap
Horwich, Bolton
Chorley
Horwich, Bolton
Minerals can only be worked where they naturally occur, so a quarry can’t just be placed wherever there’s space. As government minerals guidance explains, planning has to begin with a clear understanding of what lies below ground.
Before extraction can be planned, operators need to know where the useful rock is, how deep it runs, how thick the deposit is and whether its quality or structure changes across the site.
Geological surveys help build that picture. Their findings can shape resource estimates, extraction phases, face design, processing, water management and planning applications. They can’t reveal every underground condition, but they give quarry planners much better information to work with.
A quarry geological survey is a planned investigation into the rock and ground beneath a proposed or existing mineral site. Its purpose is to find out what is there, where it is and how conditions change across the site.
This picture rarely comes from one survey or visit. It may bring together:
The findings can then be shown through maps, cross-sections and geological models. The amount of work required depends on the deposit, the size of the site, what information already exists and which decisions need to be made.
The two can overlap, but they have different aims. A typical construction site investigation looks at whether the ground can support a proposed building or earthworks.
A quarry investigation also needs to find out what mineral is present, how much there may be, whether its quality changes and how it could be extracted.
Other surveys may support the same project. A topographical survey records the shape and levels of the land, a geotechnical assessment considers ground stability and a hydrogeological investigation looks at groundwater. Each provides different information for the quarry plan.
The investigation usually moves from existing records to work on the ground, followed by testing and geological modelling.
Mineral exploration normally begins with a desk study. Geologists may review British Geological Survey maps and borehole records, previous site investigations, historical maps, aerial images and records of former quarries or mines.
Topographical, drainage, planning and land information can add further detail. Together, these records provide a starting picture of the site and show where information is missing.
A desk study can highlight the potential for a mineral deposit, but it can’t prove that commercially workable material is present. The BGS mineral assessment records show how mapping, drilling, sampling and borehole logging have been used to investigate mineral resources around the UK.
Geologists then compare the existing records with what can be seen on the ground. They may examine exposed rock, existing quarry faces and changes between different rock types.
Features such as bedding, joints, faults, fractures and weathering are recorded, along with signs of former workings, surface water or wet ground. This helps check the early geological picture and decide where trial pits or boreholes may be needed.
Trial pits allow geologists to examine shallow ground, including the overburden above the mineral and changes close to the surface.
Boreholes provide information from greater depths. Core drilling removes sections of rock that can be logged and sampled, showing where the rock type, condition or quality changes below ground.
There’s no standard depth or spacing that works for every investigation. A borehole only shows the ground at that location, so several investigation points may be needed to understand how the deposit changes across the site.
Geophysical surveys can help investigate the ground between boreholes or across areas where digging and drilling are more difficult.
Depending on the method and site, they may indicate changes in the rock, the depth to solid ground or the possible location of faults, voids and former workings. The findings can also help target further drilling.
These surveys need specialist interpretation. They add to the evidence gathered through trial pits, boreholes and samples rather than automatically replacing them.
Finding the rock is only part of the investigation. Samples may also need to be tested to understand what the material could be used for.
Depending on the planned products, testing may look at the rock’s composition, strength, resistance to wear, water absorption, durability or chemical properties. Samples should remain linked to the place and depth from which they were taken, so any changes can be mapped across the deposit.
Our guide to aggregate testing methods used in UK construction explains more about how material properties are assessed.
The maps, observations, borehole logs and test results are finally brought together into a model of the deposit.
This may show:
The model can be presented through plans, cross-sections or 3D software. It gives quarry planners a much clearer view below ground, although it remains an interpretation of the available evidence rather than an exact picture of every part of the deposit.
The geological model can help estimate how much mineral lies within the area investigated. However, the total volume of rock underground isn’t the same as the amount of saleable aggregate a quarry can produce.
Estimates may need to allow for overburden and unusable layers, changes in rock quality, extraction boundaries and stand-off areas. Some material may also need to remain within faces or benches. Processing losses, likely product yield, access and water can reduce the workable amount further.
The geological resource is the starting point. Planning permission, quarry design and practical or commercial limits all affect how much can become a workable reserve. Our guide explains more about how quarry reserves are managed and planned long-term.
Survey findings can shape decisions throughout the life of a quarry:
| Survey finding | Quarry decision it may inform |
| Depth and extent of the deposit | Working boundaries, extraction phases and resource estimates |
| Changes in rock quality | Selective extraction, blending, processing and potential products |
| Overburden or unsuitable layers | Stripping, material handling and expected yield |
| Bedding, joints and faults | Face direction, bench design, stability work and blasting plans |
| Weathered or weakened rock | Different working methods or further investigation |
| Groundwater conditions | Drainage, dewatering and water monitoring |
| Voids or former workings | Further assessment, exclusion areas or changes to the design |
Geology is only one part of the final quarry plan. Land ownership, planning boundaries, environmental constraints, access, safety and demand for the finished products must also be considered.
The way rock is layered and fractured affects how it breaks during extraction. Bedding, joints and faults can create natural weaknesses, while weathering and water may make some areas less stable.
This information can influence the direction and height of quarry faces, the width and position of benches and the limits of excavation. It may also affect blasting, drainage and the type of plant used to extract and handle the rock.
The HSE’s quarry-design guidance explains how the geology and geotechnical features of a site help determine how it should be worked.
A geological survey provides useful evidence for safe design, but it doesn’t automatically replace a formal geotechnical assessment. Any duties under the Quarries Regulations and the HSE Approved Code of Practice should be considered by the appropriate specialists.
Geological evidence can help show what mineral is likely to be present, how far it extends and why a particular working area has been chosen. It may also support proposed extraction phases and identify issues involving overburden, ground stability, water and restoration.
The findings can feed into separate environmental, hydrogeological and geotechnical assessments as the proposal develops.
Finding a suitable deposit doesn’t guarantee planning permission. The mineral planning authority must also consider matters such as landscape, ecology, traffic, noise, dust, water and effects on the surrounding area.
The information required will depend on the site and the authority assessing the proposal. Government minerals-planning guidance explains these wider considerations.
No. Boreholes, trial pits and samples only reveal conditions at selected locations. Geologists use that evidence to interpret what may lie between them, so every geological model contains some uncertainty.
Confidence depends on how many investigation points are available, how well they’re spread across the site and how complex the geology is. The quality of earlier records and the consistency of test results also matter.
Once extraction begins, newly exposed faces provide more evidence. Further mapping, sampling or investigation can then be used to update the model and adjust future working plans.
This doesn’t make the original survey invalid. It builds on the starting picture as more of the deposit becomes visible.
Geological surveys give quarry operators a clearer picture of what lies beneath a site before major planning and extraction decisions are made. They support resource estimates, safer quarry design, product planning and decisions about water, overburden and unsuitable material.
Their value doesn’t end when the first report is complete. Comparing the model with newly exposed rock helps operators refine it and plan later phases using better information.
Explore Armstrongs’ aggregate range or read more about how quarry reserves are managed and planned long-term.
It’s a planned investigation of the rock and ground beneath a proposed or existing quarry. It uses records, site observations and physical investigation to build a picture of the deposit.
Geology helps operators understand where useful rock may be found, how its quality changes and which areas could be more difficult or unsafe to work.
Methods may include desk studies, geological mapping, trial pits, boreholes, core sampling, geophysical surveys and laboratory testing. The right combination depends on the deposit and the information needed.
Boreholes reveal conditions below the visible surface. They can show the depth and thickness of the deposit, along with changes in rock type, quality or condition.
Testing samples can provide strong evidence about likely quality and potential uses. However, quality may vary across the deposit, so further sampling may be needed as extraction progresses.
A geological survey looks at the deposit, including its rock types, structure and variation. A geotechnical assessment focuses more closely on how the ground may behave and remain stable during quarrying.
Geologists use mapping, investigation points and measurements of the deposit’s depth and thickness to estimate its volume. Allowances are then needed for unusable material and practical working constraints.
Yes. Newly exposed faces, production results and further sampling provide more information, allowing the geological model and future working plans to be updated.
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