Introduction

Particle size is a fundamental property of sedimentary materials that may tell us much about their origins and history. In particular the dynamical conditions of transport and deposition of the constituent particles of rocks is usually inferred from their size. The size distribution is also an essential property for assessing the likely behaviour of granular material under applied fluid or gravitational forces, and gauging the economic utility of bulk materials ranging from foundry sands to china clay.

Among solid bodies only a sphere has a single characteristic linear dimension. Irregular sedimentary particles possess many properties from which several characteristic linear dimensions may be obtained. These include a particle's projected area, settling velocity, volume, lengths, and the size of a hole through which it will pass. These dimensions are, of course, not equivalent, save in special circumstances (e.g., for a sphere), a fact which is generally appreciated but usually overlooked. Krumbein & Pettijohn (1938) give a detailed analysis of the properties used as measures of particle size. Their book is the reference for all that we shall refer to as “classical” in this chapter. There is a huge variety of commercially available instruments, but we have not attempted to list them all (but see the appendix for names and addresses). A concise survey of the state of the market in 1987 was provided by Stanley-Wood (1987a) and a little earlier by Bunville (1984).