A mineral that forms only under specific pressure and temperature conditions, and that therefore provides information about the metamorphic history of the rock in which it is found. The minerals kyanite, andalusite, and sillimanite are examples of index minerals.
noun, Statistics. 1. a quantity whose variation over a period of time measures the change in some phenomenon. noun 1. (statistics) a statistic indicating the relative change occurring in each successive period of time in the price, volume, or value of a commodity or in a general economic variable, such as the price level, national […]
- Index of industrial production
noun 1. (in Britain) an index produced by the Central Statistical Office showing changes in the production of the primary British industries
noun, Optics. 1. a number indicating the speed of light in a given medium as either the ratio of the speed of light in a vacuum to that in the given medium (absolute index of refraction) or the ratio of the speed of light in a specified medium to that in the given medium (relative […]
noun, Machinery. 1. a plate perforated with rows of different numbers of equally spaced holes as a guide for indexing work.