The codes and descriptions used in the BGS Rock Classification Scheme (RCS) are derived from a series of reports written by BGS staff. These reports contain the detail and reasoning behind the names used and should be consulted. These are freely available and may be downloaded from this site.
New names are added to the RCS as required. All new names follow the rules and conventions described in the BGS reports.
The RCS naming structure is hierarchical. Non-alphabetic characters at the start of the code identify high-level names in the hierarchy. For example the highest levels are TOP OF HIERARCHY, with the code +, and ROCK AND SEDIMENT with the code +@RSD.
Policy is that non-alphabetic character codes must not be used to identify rock or sediment types within coded digital data such as borehole logs or digital map polygons.
Dr Tim McCormick is the first contact for more information.