Brucite after Periclase

specimen number:
2354181

location:
Crestmore Quarries, Riverside Co., California, USA

description:
Many grains of what were once periclase measuring to 0.2 cm in size, these now replaced by brucite and scattered richly throughout matrix.

Located near Riverside, California, the Crestmore Quarries are world-famous contact-metamorphic localities where Jurassic-to-Cretaceous quartz diorite and quartz monzonite plutons intruded Paleozoic limestone and dolomite rocks. Commercial quarrying began in the early twentieth century by the Riverside Portland Cement Company to produce limestone for cement and industrial aggregate, continuing for several decades. Thermal metamorphism created complex skarn deposits and calc-silicate hornfels containing over 150 distinct mineral species, including numerous type-locality minerals such as crestmoreite, riversideite, plombierite, and tilleyite. Over the decades, thousands of amateur collectors, professional mineralogists, and academic researchers visited the open pits and underground workings to collect well-crystallized specimens until safety concerns and industrial site closures curtailed public collecting access in the late twentieth century.

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