| Webster's Online Dictionary |
| Expressions | Domain | Definition | |
| Index mineral | Mining | A mineral developed under a particular set of temperature and pressure conditions, thus characterizing a particular degree of metamorphism. When dealing with progressive metamorphism, it is a mineral whose first appearance (in passing from low to higher grades of metamorphism) marks the outer limit of the zone in question. Cf: typomorphic mineral. (references) | |
| Metamorphic index mineral | Mining | One of a set of minerals found in metamorphic rocks and used as indicators of the temperature and pressure conditions at which the metamorphism occurred. A metamorphic index mineral is stable only within a narrow range of temperatures and pressures, and the metamorphism that produces it must take place within that range. (references) | |
Source: compiled by the editor from various references; see credits. | Top | ||
