Manjiroite

specimen number:
2354310

location:
Prompter Mine, Cochise Co., Arizona, USA

description:

Lustrous black massive manjiroite on matrix. Good example for the species. Collected by David Shannon in April, 2000.

The Prompter Mine in the historic Tombstone Mining District of Cochise County, Arizona, exploits complex tabular replacement orebodies hosted within Paleozoic Naco Group limestone along the footwall of the local Prompter Fault zone. Historically operated for gold, silver, and manganese, this underground network yielded various supergene manganese oxide minerals within its highly oxidized zone. Among these rare finds is manjiroite, a hydrated sodium-bearing manganese oxide that forms dense, dark, massive aggregates or microscopic fibrous clusters resulting from low-temperature secondary alteration processes. Mineral collectors prize specimens from this locality due to the scarcity of well-documented American occurrences of this unusual tunnel-structure oxide.

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