OR/15/039 Technical information

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Linley, K A. 2015. User Guide Mining Hazard (not including coal) v7. British Geological Survey Internal Report, OR/15/039.

Source of information name

The data is drawn from a broad range of sources. The underlying geology (as polygon areas) is derived from BGS 1:50 000 scale DiGMapGB (the digital geological map of Great Britain) version 7. Details of additional locations and criteria used to refine areas of working have been sourced through BGS experts and extensive literature research. A condensed list of the references used is provided.


The Mining Hazard (not including coal) data has been developed at 1:50 000 scale. The data is not suitable for use at larger scales. It should be recognised that using the data at a scale of greater than 1:50 000 is beyond the accuracy of the underlying geological map data from which the mining hazard data is partially derived. In carrying out spatial searches against the data it is recommended that this should be done with a minimum 50 m buffer.

Creation of the dataset

Great Britain has a long and varied history of underground mining. Over the last five thousand years a range of over fifty different minerals have been extracted leaving underground spaces or voids. Table 1 lists the commodities included in the dataset and worked as part of this long and varied mining legacy.

Because of the broad range of commodities, their different modes of occurrence and extraction, the commodities were grouped into seven categories with shared characteristics:

  1. Vein Minerals includes copper, lead, zinc, tin
  2. Chalk
  3. Oil shale
  4. Building stone including limestone, sand, sandstone, slate
  5. Bedded ores including iron ores (haematite), manganese, sulphides
  6. Evaporites including gypsum, anhydrite, potash, salt
  7. Other commodities — small locally worked materials including ball clay, black marble, jet, graphite, chert

A methodology was devised for each separate group. The categorisation was based on local geological factors, expert knowledge and detailed research from literature. Whilst the methodologies were broadly similar, with the distribution of commodities being constrained by geological distribution, local or market factors play a significant part in where materials were worked. Examples include:

  1. Chalk — because of its widespread distribution and low value, material would not have been worked in areas below the water table
  2. Building stone production — constrained by economic factors such as distance to end use and accessibility to transport infrastructure. These form constraining factors on where material was worked
Table 1 Commodities included in the Mining Hazard data
Commodity Commodity Commodity
Anhydrite Hearthstone Potash and salt
Anhydrite and gypsum Hornstone Raddle
Ball clay Iron ‐ Ochre Ragstone (Kentish)
Barite (Bedded) Iron Ore (Bedded) Salt ‐ brine
Bauxite Iron Ore (Non Vein) Salt ‐ Rock salt
Bedded Ore (Manganese) Jet Salt ‐ salt and brine
Black Marble Lead Sand
Chalk Lignite Sand ‐ Glass making
Chert Limestone Sand & Gravel
Chromite Limestone ‐ Ardwick Sand Rock
Clay Limestone ‐ Bath Stone Sandstone
Copper Limestone ‐ Beer Stone Sandstone ‐ Chilmark Stone
Fireclay Limestone ‐ Black Country Sandstone ‐ Elland Flags
Firestone Limestone ‐ Burford Stone Sandstone ‐ Flagstones
Flagstone Limestone ‐ High Purity Silica
Flint Limestone ‐ Ketton Stone Slate
Fullers Earth Limestone ‐ Lincolnshire Slate ‐ Colleyweston
Ganister Limestone ‐ Portland Sulphide (Bedded)
Graphite Limestone ‐ Purbeck Talc
Gritstone Limestone (hydraulic) Vein Mineral
Gypsum Manganese (Bedded) Whetstone
Gypsum and anhydrite Oil shale Whinstone

Where mitigating criteria are known to influence location and extent of mining they have been used to constrain the mining areas shown in the data. Where no supplementary information is available the full geological coverage has been retained.

Initial processing resulted in seven separate data layers. The contents of each layer are classified against a single A–E classification scheme. This standardisation ensures for example that a C rating for vein minerals is equitable with a C rating for chalk.

Having created the seven separate data layers (vein minerals, chalk, oil shale, building stones, bedded ores, evaporites, other commodities) they are brought together into a single comprehensive mining hazard layer. A simplified version of the iterative integration process is given in Figure 1 Iterative process for combining data layers.

All data processing and spatial data checking has been carried out using ESRI ArcGIS software.

Figure 1 Iterative process for combining data layers.

Table field descriptions

Table 2 describes the attribute table fields.

Table 2 Attribute table field descriptions
Field name Field description
SHAPE Necessary for the ESRI shapefile format indicating polygon data.
CLASS Polygons are classified using an A–E scale ( see Class descriptors)

Where mining of more than one commodity has occurred at a location the highest class is applied to a polygon for example a polygon with a building stone rating of B and a vein mineral rating of E is given a class E rating.

See Note 2

LEGEND Brief description of classes, for more detailed explanation see Class descriptors.
COMMODITY Commodity describes the material worked for example chalk, sandstone. Where these can be subdivided for example Limestone‐Black Country, Limestone‐Bath Stone, Limestone — Burford Stone.

Where information is available on the commodity worked it is recorded here e.g. Bath Stone, limestone, brine.

Note 1 and Note 3

COMMENTS Within the chalk the location of some known workings is only available within a 1 km grid square. These grid cells have been flagged with a comment to show that mining is known in this area but the exact location is unknown.
NAME This is the site name where available. For some data types for example building stones the sites specific names e.g. Bethel, Draycott‐in‐the‐Moor, and Ewe Crag this is shown.

For other commodities and the majority of localities the data represents unnamed occurrences. In these cases the field is populated with ‘Not available’.

Where a site has been given more than one name (often when more than one commodity has been worked) e.g. Dalry/Glenarnoch both site names are given.

See Note 1

VERSION Mining Hazard not Including Coal for Great Britain v7.
Note 1

Where more than one commodity occurs at a location both are shown e.g. Vein minerals/Building stone.

The order also applies to the Name field i.e. Name = Dalry/Glenarnoch Group = Vein Minerals/Building stone Dalry is a vein minerals location whilst Glenarnoch is the building stone location name.

Note 2

If a site lies within a rated polygon, it does not necessarily indicate the presence of mining, rather the likelihood of past mining to have occurred. In these cases it is recommended that further enquiries are made regarding the potential for past mining activity.

Note 3

Where no information is available a description of ‘Not available’ it indicates that no value has been found.

Dataset history

The original version of the Mining Hazard (not including coal) GB V1 was released in February 2009.

Since then work has continued to develop with an updated version of Mining Hazard (not including coal) GB V5 release in July 2010. The version 5 release included:

  • Inclusion of more building stone locations
  • Re-working of the chalk methodology to provide improved coverage
  • Re-design of the vein minerals methodology to produce a more focused and representative extent for this set of commodities

Early in 2014 a number of mining related ‘sink hole’ events occurred. As a consequence a small number of revisions have been made to the Mining Hazard (not including coal) dataset. These revisions resulted in the release of an interim Version 5.1.

The version 5.1 update concentrated on generalisation of some of the known chalk localities in the South East of England. To reflect the change in the geometry of the data, a comments field has been included in the attribute table to record chalk localities where only an approximate grid reference is available but no further detail. These grid references are accurate to within 1000 m grid square in these cases the whole grid square was tagged with a comment to indicate that chalk workings are known at that locale but that no more specific information is available.

In 2015, version 7 of the dataset was released. Updates focussed on redevelopment of the chalk methodology. This work was carried out as a consequence of the sink holes which occurred in early 2014. Whilst many of the sink holes were of natural origin i.e. dissolution events linked to climate i.e. dry summer followed by wet winter conditions; several of the collapses included an anthropogenic influence through association with former mining locations.

Additional work has been carried out to identify new and refine existing locations from literature and these have been integrated into the existing data.

Note: In 2008 BGS introduced its new versioning system whereby the version number of the dataset relates to the version of DiGMapGB-50 base data, the original version of Mining Hazard (not including coal) was released as version 1 but to comply with the new naming practice it has jumped from Mining Hazard (not including coal) version 1 to version 5 and subsequent versions relate to the version of DiGMapGB 50k the base data was drawn from.


Data coverage includes England, Scotland and Wales. For data distribution see Figure 2.

Data format

The Mining Hazard (not including coal) data has been created as vector polygons and are available in a range of GIS formats, including ArcGIS (.shp), ArcInfo Coverages and MapInfo (.tab). More specialised formats may be available but may incur additional processing costs.


  • Most geological maps were originally fitted to a particular edition of the topographic base and care must be taken in interpretation, for example when the geological data are draped over a more recent topography. All spatial searches against the data should be done with a minimum 50 m buffer.
  • The observations made in the production of this data are according to the prevailing understanding of the subject at the time. The quality of such observations may be affected by subsequent advances in knowledge, improved methods of interpretation, and access to new sources of information.
  • Raw data may have been transcribed from analogue to digital format, or may have been acquired by means of automated techniques. Although such processes are subjected to quality control to ensure reliability where possible, some raw data may have been processed without human intervention and may in consequence contain undetected errors.
  • Data may be compiled from the disparate sources of information at the BGS's disposal; including material donated to the BGS by third parties, and may not have been subject to any verification or other quality control process.
  • Data, information and related records which have been donated to the BGS have been produced for a specific purpose, and that may affect the type and completeness of the data recorded and any interpretation. The nature and purpose of data collection, and the age of the resultant material may render it unsuitable for certain applications/uses. You must verify the suitability of the material for your intended usage.
  • The data, information and related records supplied by the BGS should not be taken as a substitute for specialist interpretations, professional advice and/or detailed site investigations. You must seek professional advice before making technical interpretations on the basis of the materials provided.
  • If customers are uncertain about the use of particular data they should seek professional advice. They may consult the BGS contacts listed at the end of this document on technical matters, licensing arrangements, or geological aspects including the appropriateness and limitations of the data.
  • Although there are a number of sites affected by underground mining where remediation has occurred including parts of the Northwich salt field, Barrow-on-Soar, Coalbrookdale, Dudley and Bury St Edmunds, the impact of this remediation work is not considered in this assessment and all ratings are given as if localities are unremediated.
Figure 2 Coverage of the Mining Hazard (not including coal).