Cookeite

specimen number:
2133204

location:
Greenwood, Oxford Co., Maine, USA

description:
Sparkling micaceous crystals of cookeite on all surfaces of this matrix. A good example for the species.

Cookeite is a relatively rare lithium-rich mineral belonging to the chlorite group, first described in 1866 and named after the American chemist Josiah Parsons Cooke. Geologically, it primarily forms as a late-stage hydrothermal mineral in lithium-bearing granite pegmatites, where it often appears as a replacement or coating on other minerals like lepidolite, spodumene, or quartz. It is typically found as small, pearly-white to pale pink or green micaceous flakes or as distinctive rounded, pseudo-hexagonal "books" and rosettes. While not mined as a primary ore for industrial lithium, its presence is a significant indicator for collectors and geologists of highly evolved pegmatite systems. Significant historical and modern occurrences include the pegmatites of Maine and California in the United States, as well as localities in Brazil, Russia, and the Pakistan-Afghanistan border regions.

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