HELENC. KERBEY ANDJANA M. HORA´ K
Mineralogy and Petrology Section, Department of Geology, National Museum Wales, Cardiff, CF10 3NP, UK
Abstract.—The Department of Geology at the National Museum of Wales (NMW) holds about 66,000 rock and mineral specimens. The NMW Collection Policies (2000) and pre- vious in house condition surveys (Lambert 1994, Buttler 1995) have been used to develop specific standards to maintain a high level of collections care and provide a baseline for future improvements. A pre-acquisition, collection impact assessment determines specific conditions or levels of care needed. Specimens are identified using a variety of visual and analytical techniques and according to international standards of nomenclature for minerals (Hey Classification) and igneous rocks (IUGS). These standards form the basis for the organisation of the collection, which is housed in oak cabinets, roller racking and on low- level pallets. Inert packaging such as Corex威and Tyvek威is utilised when required. Storage conditions are set at 18–23⬚C and 45–55% RH with exceptional cases stored in customised microclimates. Seven hundred and fifty radioactive specimens are now stored in a special isolation store. Two hundred and eighty-eight mineral species are being monitored due to UK COSHH health and safety regulations. Pest monitoring is due to become routine in 2006 and the planned new storage areas will improve physical access whilst maintaining these standards of collection care.
INTRODUCTION
The National Museum of Wales (NMW) was founded by Royal charter in 1907 and is a multidiscipline institute spread over eight sites across Wales. The Museum receives its core funding through grant-in-aid from the Welsh Assembly Govern- ment and has custodianship of more than four million items, which include objects and specimens as diverse as a Welsh chapel, impressionist paintings, and the world’s largest leatherback turtle. These are organised into nine main collection areas that are managed by five curatorial departments and the NMW Library. The geological collections are housed in the capital city of Wales, in the National Museum, Cardiff, and comprise approximately 400,000 accessioned specimens, divided into three main areas, palaeontology, petrology and mineralogy. All spec- imens are documented on an electronic database, part of an electronic collection management system Sn-Base, a natural science version of the Mobydoc, Micro- muse´e system. The approximately 66,000 mineralogy and petrology specimens range from hand samples and microscope thin sections to borehole core, display quality minerals, gemstones and meteorites, and are supported by three curators, a collection manager, and a geological conservator. The overarching management, care, and use of NMW collections is guided by the National Museum of Wales Collection Policies (NMW 2000) which support the Museum in its aim to be ‘the best possible repository for the collections of national renown and importance held in care for Wales’. These policies are then implemented by a set of seventeen generic Collection Management Procedures, which are customised for each col- lection-area to include collection specific details. Further details of these policies and procedures are provided by Howlett & Hora´k (this volume) and the policies
themselves are available on the internet (NMW 2000). Information produced in the course of routine collection-based work at NMW is used to provide museum- wide performance indicators (such as number of items electronically catalogued) that serve as a useful guide to improvements in standards of curation.
This paper outlines these standards and how they have been implemented with- in the petrology and mineralogy collections to achieve and maintain the aims of the museum.
EVALUATINGACCESSION STANDARDS
Collection Impact Assessment
The first stage in the effective management of the collections starts prior to formal acquisition of specimens with a Collection Impact Assessment (CIA). This evaluates the resources required to store, conserve, and curate the specimens under consideration and these data are documented on the CIA form. Where the impact is evaluated and considered acceptable, the form becomes part of the acquisition proposal documentation. The current version of the CIA form was introduced across all NMW collection areas in 2004, to ensure that the implications of and the reason for accepting any acquisition, no matter how small, is considered fully.
It also allows detailed costings associated with post-acquisition work (e.g., cura- tion, documentation, conservation, and storage) to be itemised. This is particularly important where significant costs are associated with larger collections, or an individual specimen requires intensive treatment or highly specialised storage. The form is completed by the relevant Collection Manager, along with a recommen- dation to acquire or not acquire, and then is authorised by the Head of Section.
Where the CIA Form recommends acquisition of items valued at more than £500 a higher level of authorisation is required (typically by the Keeper). The current version of the form will be reviewed in 2006, with a proposal that the current Department of Geology procedure of hazard checking be formally added. An example based on a recent mineral donation to NMW is shown in the appendix.
Risk Assessment
Of particular pertinence to mineralogy and petrology specimens, is a risk as- sessment to identify potential hazards presented by the specimens. Although the impact of pests is mentioned within the Museum-wide Risk Assessment Proce- dures, no comprehensive pest surveying at acquisition stage is undertaken at pres- ent. This is currently under review within the Department of Geology. Materials originating from foreign fieldwork programmes and collections that may have been subject to infestation prior to acquisition, are considered the highest risk. To remedy this, a new collection surveying area, allowing collections to be quaran- tined during pest testing, is planned, and will be in operation in 2006.
In addition, testing for radioactivity is undertaken on all incoming material, and the likely presence of carcinogenic and toxic minerals evaluated. Such specimens are not necessarily excluded from the collections. However, rigorous evaluation of the benefits of acquisition is required. If accepted, such specimens are given specialised packaging, labelling and secure storage (see below). All unidentified specimens are treated with caution until their composition is known.
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Condition Report and Surveys
As a result of a major conservation review of the geological collections that was started in 1989 (Buttler 1995), it is a requirement that a Condition Report (Fig. 1) is prepared by the Geological Conservation Officer for all possible ac- quisitions to geology. The condition report states the environmental conditions most suitable for the specimens and any special packaging requirements. It is presented in a written form though the terms used such as ‘slightly dirty’ or
‘moderate damage’ are taken from a quantitative scale used for surveys (Buttler, 1995) and described in more detail in the conservation section below. Using descriptive terms for the report enables it to be understood by a wider audience once it becomes part of the documentation for the specimen.
Whilst identified specimens can be evaluated easily, unidentified specimens can be assessed only on visible signs of instability, such as friability or the smell associated with pyrite decay. Scientific knowledge can also be used, for example a rock composed of silicates is more likely to be stable than a rock containing crusts of secondary mineralization, or particular localities may be flagged up as yielding unstable specimens. Where specimens are unidentified, but of possible high scientific value, for example a potential new mineral occurrence, identifi- cation may be undertaken as part of the Risk Assessment and prior to the Con- dition Report. This process is facilitated greatly by access to modern X-ray dif- fraction and Fourier Transform Infrared Spectroscopy (FTIR) facilities at the NMW. As a precaution against any deterioration, unidentified collections are stored in a controlled environment from the time they arrive in the Museum and a rolling condition-checking program is in place that should detect specimens that show signs of change in condition.
Where particularly large collections require condition reporting, this can be done by representative sampling. For the Buttler conservation survey undertaken to establish a baseline for the NMW mineral collection (Buttler 1995), sampling was achieved by evaluation of the specimen at the front left of every drawer.
Whilst this works well for the collections stored at the NMW by chemical clas- sification it will be less representative for collections that are not sorted on a chemical basis; for example, if the collection is being assessed at the donor’s address in its original storage arrangement. In these cases, assessment may have to involve checking a greater proportion of the collection and will rely heavily on visual assessments. Detailed information on effective sampling for condition surveys is given in Keene (1991).
DOCUMENTATIONSTANDARDS Identification and Terminology
The NMW mineral collection is organised according to the Hey’s Mineral In- dex, 3rd Edition (Clark 1993) and using the International Mineral Association, Commission on New Mineral and Mineral Names (CNMMN 2006) approved terminology. All specimens are identified by naked eye and using optical mi- croscopy. However, improvement in the range of non-destructive analytical equip- ment available to curatorial staff means that a higher level of non-destructive techniques are increasingly applied, particularly to the core Welsh mineral col- lection. For instance, FTIR is used at NMW, particularly in the rapid identification
Figure 1. A composite example of a condition report constructed from several recent acquisitions.
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of organic substances, sulphate, and carbonate group minerals, as this requires only a small powder sample. New X-ray microdiffraction facilities enable rapid and non-destructive identification of small minerals and some rock samples. Iden- tification of specimens from Welsh localities is also made by comparison to a known ‘encyclopaedia’ of mineral data, as presented in A Mineralogy of Wales (Bevins 1994) and shortly to be available online in a greatly expanded and up- dated version, via the NMW website (NMW 2005). New mineral species and specimens identified only to a mineral group or family level are not found in the Hey 3rd Edition, and so are stored alphabetically in a Non-Hey section of the collection, until a revised version of the Index is produced. In reality, the number of specimens held in this section is small so this does not present an inconve- nience.
Within the petrology collection, igneous rocks are named following the IUGS Subcommission on the Systematics of Igneous Rocks (SSIR) nomenclature (Le Maitre 2002). This is not ideal for volcanic rocks where a whole-rock geochemical analysis is not available, but works well with plutonic and hypabyssal rocks, as thin sections can be prepared to confirm the mineral composition and abundance within a specimen. Specimens sometimes have obsolete names that no longer fall within this classification, often with a regional connotation and significance. For example, Skomerite is found on Skomer Island, off the coast of southwest Wales.
These are renamed and the original name retained and recorded under a designated
‘original data’ database field. Although the IUGS Subcommission on the System- atics of Metamorphic Rocks (SCMR) has produced recommendations for the nam- ing of metamorphic rocks (SCMR 2004) this has yet to be adopted by the NMW.
A simple, but consistent, nomenclature has been used, based on texture and min- eral composition. However, the new classification will be introduced when doc- umentation resources permit. A similar situation exists with sedimentary rocks within the NMW collection, as a sedimentary rock classification scheme is yet to be produced by the IUGS, Commission on Petrology. NMW terminology is based on grainsize and composition and loosely follows the nomenclature used by the British Geological Survey (BGS 1999). Where a colloquial or trade name for a rock is known such asCampan vert(mottled limestone marble),Stonesfield Slate (calcareous sandstone)Doulting stone (Jurassic limestone) or Gwenith faen goch (red sandstone), it is recorded in a dedicated database field, alongside the scientific term, and can be particularly useful when dealing with public enquires or ac- cessing older scientific literature.
Document Curation
The Geological collections at NMW include many documents such as maps, field slips publications, and correspondence. There is a specialist Archive store and map room for historical items and every acquisition has a ‘history folder’
where Collection Impact Assessments, Condition Reports and related information are stored in paper form. As well as an electronic catalogue, all specimen details are recorded on hard copy registers and these along with items such as original transfer of ownership forms are kept in a fireproof safe. As an additional measure all pre-1995 register details are held in the central museum archive on microfiche.
STANDARDS OF STORAGEANDCARE Minerals
The mineral collection is arranged according to the Hey System 3rd Edition (Clarke 1993) in a Bruynzeel Monta Mobile System of roller racking (Howe 1987) necessitating only a few extremely large specimens to be stored on static shelving elsewhere in the room. Environmental conditions, whilst not an issue to most of the petrology specimens, are typically set at 18–23⬚C and 45–55% RH to suit the majority of specimens, based on guidelines given by Thomson (1978), and Howie (1992). The most important factor is the stability of the climate hence these con- ditions are controlled by an air conditioning unit. At the NMW some problems have been experienced in maintaining optimum storage conditions in this storage area as a result of plant failure and this has for time to time resulted in temperature fluctuations. These fluctuations have in part also been attributed to possible ex- ternal input of heat to the store from heating pipes and may be resolved by producing a thermal imaging map of the room to identify the location of ‘hot spots’ and allow vulnerable specimens to be relocated to more stable lower risk positions within the storage units.
The introduction of roller racking increased capacity within the storage area by over 110%. However, the condition survey (Buttler 1995) identified abrasion as a major or potential cause of damage amongst the mineral specimens, directly resulting from specimen movement when the roller racking was operated. As a result, all minerals have been repacked using chemically inert polyethylene foam (e.g., Plastazote
威
), and all new additions are now carefully packed in high-sided trays with acetate lids. To prevent the trays from sliding any spaces within a drawer are filled with empty card trays.Access to collections held by the Department of Geology is governed by the NMW Access Policy and implemented by a department-specific Access Proce- dure. This supports the balance between the maximising the use of the collections with their long-term preservation. On a practical level the procedures dictate that;
only staff working on the mineralogy and petrology collection have access to these storage areas, that all external visitors and users are supervised at all times, and that the details of visits to the stores are logged. Access to both the geological stores and the roller racking within them, is controlled by keys, which are held by a restricted number of geological staff. The stores have signs on the door reinforcing these access rules and providing emergency contact information.
Petrology
Rocks are stored by geographical subdivisions (e.g., Wales, England) and with- in each of these sections by acquisition order. Although this may appear a highly unsophisticated system, all specimens are held on electronic inventory so this has proved the most efficient method of access. Hand specimens are stored in acid- free trays in closed, static oak cabinets. No environmental problems have been identified from the use of oak cabinets, although in exceptional circumstances microclimates are used for rocks containing evaporate minerals or pyrite. Though the oak cabinets appear to provide a satisfactory method of storage, access and health and safety considerations have lead to the collection being included within NMW’s plans to relocate the petrology collections to new roller racking at an off-
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Figure 2. A hand-made Corex威box for protecting a large petrology specimen from abrasion and dust.
site store. Where possible, larger specimens are incorporated with the specimens within the cupboards and roller racking. However, those that are too large are stored in hand-made Corex
威
boxes (Fig. 2) or fitted with custom made Tyvek威
covers (Fig. 3) to protect against abrasion and dust. These materials were chosen because they are sufficiently strong to accommodate all but the largest petrology specimens; they are relatively cheap; and they can be manipulated easily and quickly into customised boxes or dust covers by curatorial staff.Thin Sections
Thin sections are stored horizontally in wooden cabinets, with polished thin sections placed in small plastic bags so that their surfaces can be protected. Pol- ished ore blocks frequently contain sulphides and are prone to extremely rapid tarnishing after polishing. To slow down this process they are stored in desiccator- style, stainless steel cabinets with environmental control provided by conditioned silica gel at 30%RH. All specimens are organised by accession number into Welsh and non-Welsh collections. As with the rock collections, all specimens are held on an electronic inventory and full acquisition details can be rapidly obtained.
Borehole Cores
The Museum holds approximately 200 borehole cores, mainly from less than 100m boreholes, or significant stratigraphic sections relating to Welsh geology.
The cores are acquired typically in large wooden crates like a recent addition from Llandegfedd, near Usk, which forms part of a Ph.D. thesis collection (Fig.
Figure 3. A Tyvek威cover protecting a large calcite crystal from dust and abrasion.
4). As core may have been stored in a less than ideal environment prior to ac- quisition (e.g., evidence of rat infestation has been noted in some older core boxes), all core is cleaned and repacked into standard one metre long card boxes of an appropriate cross-section. This reduces the potential pest hazard presented by the boxes, and the health and safety hazards associated with handling the core.
The standard core boxes are stacked uniformly on pallets which allow individual boxes to be moved by hand and a pallet of cores to be manoeuvred with a pallet truck by a single member of staff. The height of each pallet is set to no more than 0.5 m to prevent the bottom boxes being crushed and ensure that the pallet truck or handling weight limits are not exceeded. A space saving system of ver- tical pallet stacking on dedicated racks is planned for the new off-site store, the construction of which is due to commence at the end of 2006.
Preventative Conservation
The Buttler conservation survey (Buttler 1995) determined that the geological collections at NMW were most at risk from six factors: abrasion, dirt, pyrite decay, efflorescence, delamination and light damage. These factors as well as packaging, stability, conservation and general condition were all assessed quan- titatively for each specimen sampled. For example, the quantitative scale used for the ‘Dirt’ category was 1: clean, 2: slightly dirty, 3: moderately dirty, and 4:
extremely dirty. A quantitative survey provides a valuable baseline for measuring changes and this survey has been useful for monitoring the status of the pyrite