GUIDELINES FOR THE CURATION OF GEOLOGICAL MATERIALS

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strength. Dental silicone moulding agents, such as 'Reprosil', are extremely expensive but very useful if a mould or impression is required quickly; the cure time is about 20 mins. Unlike the previous two produces mentioned, 'Reprosil' cannot be used to take numerous resin casts since it breaks down, particularly with epoxy resins. Rubber (e.g., Dunlop A600) Latex is useful for peels and for field work but is quite incompatible with resins; casts should not be taken from peels or moulds composed of latex. Hot, melted polyvinyl chloride-based moulding compounds such as 'Vinamould' are seldom used now, the detail is not good and the concept of pouring a very hot (150°C) liquid over fossil material is not a good one; in addition their use poses a health hazard. 2.3.3. Storage of moulds Dow Corning and Wacker moulds appear to last up to about 5 years before showing signs of deterioration, usually becoming increasingly brittle. It is thoughi that this can be improved by heat-curing moulds, but this is not yet adequately proved. Latex peels store indefinitely but become tacky and brittle. They are best stored dusted with talc and with polythene between them to prevent sticking to each other. Plaster and glass-reinforced plastic (GRP) casts store indefinitely. Moulds and casts are stored in the same conditions as the fossil collections (temperatures range 15"C-25"C and rh 30% to 60% though this may prove to be slightly too warm an environment for silicone rubber. A cool, dry dark place 1s the optimum environment for the storage of all moulds composed of silicone rubber. ENVIRONMENTAL CONTROL A large number of geological materials are sensitive to certain components of the environment viz: Relative humidity (rh) Temperature Atmospheric chemicals Light Vibration Section C2.4.1 will detail the kinds of problems that can be encountered when variations or excesses of any of the above occur; Section C2.4.2 will specify those environmental conditions which should prevent the problems arising. Environmental monitoring is also considered. Many of these topics are dealt with by Thomson (1978). 2.4.1. The problem areas 2.4.1.1. Relative humidity (rh) variation The mineral constituents of geological material can be susceptible to chemical or physical changes in which rh plays an important role, in two kinds of reaction: Oxidation/corrosion (from simple oxidation product surface tarnishing to the
more extensive and complex corrosion of specimens involving acid reagents derived from the atmosphere or from mineral breakdown products) Hydrationldehydration (resulting in destructive dimensional changes and including efflorescence, deliquescence and hydrolysis) The corrosion of native metals, such as silver, copper, antimony, etc., or of metallic iron in some meteorites (see also C3.7.1) is brought about by a combination of factors, the principal of which is high relative humidity. The extent of corrosion ranges from surface tarnishing to serious pitting: the latter may be brought about by the presence of hygroscopic salts in intimate contact with the metal concerned or by storage in contaminated air containing traces of acid i.e. vapour. Thus acidic material must never be used in cleaning native metals. The oxidation of many common sulphides, and rarer arsenides and sulphosalts will occur readily at high or fluctuating relative humidity. The case of reactive pyrite deterioration has received much attention lately and the mechanisms involved in the oxidation of this mineral, together with other sulphides such as chalcopyrite, pyrrhotite, sphalerite and chalcocite, have been described by Howie (1979a,b), and Steger & Desjardins (1978, 1980). Pyrite decay manifests itself by the loss of surface shine, powdering of the surface with the development of white or yellow crystals and the presence of a sulphurous smell. Eventually paper below specimens turns brown and crumbles, whilst the specimen itself disintegrates. commonly from the base. The prevention of sulphide oxidation is achieved overall by the storage of material at low rh. The storage of reactive types at relative humidities of 50% or less appears satisfactory over periods of several years, whereas short periods of storage at 60% or higher results in rapid deterioration (Howie 1979, 1984). The treatment of oxidised pyrite is detailed by Rixon (1976), Howie (1979) and Cornish & Doyle (1983, 1984), the last of whom recommend the use of ethanolamine thioglycollate. Several minerals and fossilised substances are both hygroscopic and dimensionally unstable. Well known examples include sub-fossil ivory and enamel, some shales, certain clay minerals, such as montmorillonite, and the silicate chrysocolla. The alternating swelling and shrinking of clays and shales containing fragile fossil specimens will ultimately cause considerable deterioration and loss, and with hygroscopic minerals. sub-fossil bone and some high-lignite plant fossils, shrinkage. cracking, distortion and spalling off of surfaces will occur when exposed to low relative humidities. Some work on the limits of rh for such material has been done and the concensus is the storage of organic-rich materials below 40% rh is not satisfactory. Material from coastal exposures may develop surface salt crystals when in fluctuating rh. These can be washed off using de-ionised water, but with particularly fragile material, first coat the specimen with a dilute solution of PVA (see Howie 1979a). A similar looking problem with calcareous specimens is the development of a calclacite type of thread-like crystals on their surfaces (see (2.4.1.3 - Byne's disease). The crystals should be removed by gentle mechanical means and the specimen impregnated with a dilute consolidant, such as Butvar (see Howie 1979a). There are large numbers of hydrated minerals, commonly halides, which undergo constitutional changes when exposed to varying rh (see C2.2.2.1). Several water-soluble minerals tend to absorb moisture or deliquesce where rh levels are at a higher water vapour pressure than that exerted by a saturated
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A . GUIDELINES FOR THE CURATION '-
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CONTENTS Part A INTRODUCTION ACQUI
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GUIDELINES FOR CURATION OF GEOLOGI
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involved at all stages of curation
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ACQUISITION: SUMMARY AND RECOMMENDA
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environomental (i.e. site) conserva
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PRIMARY ACQUISITION: COLLECTING AND
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clearly and indelibly labelled with
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2.1.3.2. Geochemistry 2.1.3.3. Geop
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2.2.1.3. Purchase 2.2.1.4. Exchange
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2.2.2.2. Private collectors This ca
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ACQUISITION DOCUMENTATION INTRODUCT
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DOCUMENTATION OF SPECIMENS DURING P
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Against the corresponding number in
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DOCUMENTATION GENERAL INTRODUCTION
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measurements, descriptions, photogr
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Fig. 3. Cataloguing a specimen usin
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Specimen Identity Numbers may be su
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ldentn Comment Object(s) OBJECT EXA
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Cooper (1982), Mayer (1974, 1976),
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its entitlement to retain a specime
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or otherwise borrowed. Those which
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must be that in which a specimen is
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must be used. An extendible numberi
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Multiple classifications and cross-
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itself the task of describing, figu
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4.4.1.2. Minerals 4.4.1.3. Rocks ne
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4.4.2. Identity and identification
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The MDA Geology Specimen Card allow
Page 61 and 62: 4.4.2.6. Status A specimen acquires
Page 63 and 64: 4.4.3.3. Colour Colour is a notorio
Page 65 and 66: Regis, Charmouth; for Whitby, Saltw
Page 67 and 68: Redundant or shifting countries and
Page 69 and 70: 4.4.4.3. Collection This system, al
Page 71 and 72: at tracing the history and fate of
Page 73 and 74: Of immediate concern is the questio
Page 75 and 76: other information of significance m
Page 77 and 78: y documentation, development, techn
Page 79 and 80: The movement of a specimen is an ev
Page 81 and 82: When a specimen is replaced in its
Page 83 and 84: the nature of a specimen and within
Page 85 and 86: 5.4.2. The documentation of complex
Page 87 and 88: 6.1.1.2. conditions of loans a lett
Page 89 and 90: description of borrowed items (incl
Page 91 and 92: ecome separated from their accompan
Page 93 and 94: paragraphs above. It should be note
Page 95 and 96: 6.2.2.4. Outlineprocedure for dispo
Page 98 and 99: SPECIMEN PRESERVATION SUMMARY AND R
Page 100 and 101: 3.8.2. Photographic materials 3.8.
Page 102 and 103: Archives C3.8.1. The care and maint
Page 104 and 105: protection and specific treatments,
Page 106 and 107: field. The excavation of unstable f
Page 108 and 109: to storing the broken pieces unasse
Page 110 and 111: Borates. Most alter (dehydrate) to
Page 114 and 115: solution of the particular mineral.
Page 116 and 117: Fig. 11. Table of materials which m
Page 118 and 119: all exterior doors and windows requ
Page 120 and 121: locks of rock, for later laboratory
Page 122 and 123: Both the nature of the geological m
Page 124 and 125: ideal (e.g. BM(NH) London; Nat. Mus
Page 126 and 127: a considerable commitment from the
Page 128 and 129: of all of these specimens in the ev
Page 130 and 131: Stony meteorites should be doubly b
Page 132 and 133: obscure the sectioned material. By
Page 134 and 135: mould, fungi or bacteria, fluorish
Page 136 and 137: 3.8.1.4. Repair 3.8.1.5. Binding Th
Page 138: The National Reprographic Centre fo
Page 141 and 142: Museum safety OCCUPATIONAL HAZARDS:
Page 143 and 144: gives regulations for the design an
Page 145 and 146: 2.1.1. Storage 2.1.2. Display While
Page 147 and 148: mineral is a minor constituent are
Page 149: appears to be the dimensions of the
Page 152 and 153: Secondary types Figured specimens C
Page 154 and 155: USES COLLECTIONS PREAMBLE In this P
Page 156 and 157: The criteria for selection of speci
Page 158 and 159: definition of a locality here is di
Page 160 and 161: museum on completion or abandonment
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Specimen-based publications Publish
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For details of palaeontological nom
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2.4.5. Referred specimens When an a
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the visitor. Either way, it fails t
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methods but do remember the need fo
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EXHIEITIONTITLE "LOST WORLDS " UNIT
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REFERENCES AND APPENDICES
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REF 2 BRUNTON, C. H. C. 1980. The u
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REF 4 persons exposed to ionising
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REF 6 OBRUCHEV, D. V. 1964. Agnatha
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REF 8 TAYLOR, H. A. 1980. The arran
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APP 2 .Museum use. NB. These glues
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APP 4 Tufskin. Alfred Adams & Co. L
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APP 6 0 Silicones and thermosetting
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APP 8 BARBOLA MODELLING PASTE Alec
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APP 10 GAUZE, cotton (B.P.B. Absorb
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APP 12 PLASTONE self-hardening mode
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APP 14 SEPARATORS and RELEASE AGENT
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APP 16 STORAGE SHELVING Bruynzeel S
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APP 18 Road, Linlithgow Bridge, Lin
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APP 20 FERRY PICKERING BOXES LTD.,
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APP 20 FERRY PICKERING BOXES LTD.,
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FERRY PICKERING BOXES LTD., 53 Mead
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APP 22 MONEY HICKS LTD, 49 Clapham
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APP 24 SOLMEDIA LTD, 31 Orford Road
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APPENDIX 3 NATIONAL SCHEME FOR GEOL
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APP 29 a resource for internal use
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29. AVON, SOMERSET. GLOUCESTERSHIRE
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GUIDELINES FOR THE CURATION OF GEOLOGICAL MATERIALS

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