Rocks and minerals may be collected for either research, education or aesthetic reasons. The colours and crystalline forms of many minerals make them particularly attractive to collectors (Figure 4).
General rock types, their modes of formation, factors affecting deterioration and conservation were described at the beginning of this chapter. Whereas the materials described earlier in this chapter were considered stable, being used for monuments and similar structures, the many and varied samples that make up geological collections are not necessarily so.
Expressions such as ‘solid as a rock’ give the wrong impression of the stability and fragility of many materials that make up geological collections. It has been estimated for instance, that about 10% of all minerals are unstable (Howie 1992) and prone to deterioration unless adequately cared for.
One of the main purposes of this section is to alert readers of the need to care for rocks and minerals as they are often overlooked and consequently neglected because of their perceived stability.