AGENTS OF DETERIORATION IN GEOLOGIC COLLECTIONS

Geologic collections may seem to be less susceptible to deterioration than other types of natural history collections, but there are a number of factors that can contribute to their degradation.

Deterioration of objects and materials can be divided into three basic categories: physical, chemical, and biological. Physical deterioration includes changes in shape and various forms of structural damage, such as breakage, tearing, or abrasion. Many geological materials are susceptible to physical damage from moisture, temperature extremes, light, improper handling or inappropriate storage. Some materials are prone to change through chemical reaction. Metals may oxidize or tarnish, and photochemical reactions may alter some substances. The addition or removal of moisture from a specimen may affect its appearance, structure, and long-term stability. Pollutants, in the form of gases or particulates, may also react with some minerals and storage materials. Biological deterioration is caused by the activity of animals like rodents and insects, and by the presence of fungi (mold, mildew). Pests may not be attracted to geologic specimens, but they can cause damage to documents and other ancillary collections. Their presence can also produce chemical changes in storage environments.

The stability of the environment is in some ways even more important than achieving the ideal temperature and humidity levels. Rapid changes in environmental conditions over a period of time can cause significant damage to a collection.

The ideal environment for one geological material may not be ideal for others. Because it is seldom possible to provide separate climates for various parts of a collection, museum storage usually involves compromise. Extremely sensitive specimens can be isolated in micro-climate containers.

Simple improvements to collection storage, environmental conditions, and housekeeping can combine to stabilize any geologic collection with a minimum of effort or cost.