Arsentsumebite (?) after mimetite

TSNB675
Specimen
Ward's NSE
Exhibit 1. Arsentsumebite (?) after mimetite; 54 mm.
Exhibit 1. Arsentsumebite (?) after mimetite; 54 mm.
Image Credit: Malcolm Southwood
Exhibit 2. 30 mm field of view.
Exhibit 2. 30 mm field of view.
Image Credit: Malcolm Southwood
Thumbnail by 1Thumbnail by 2

Specimen Title

Arsentsumebite (?) after mimetite

Associated Minerals

anglesite; arsentsumebite (?); gartrellite (?)

Principal Mineral

Arsentsumebite

Precursor Mineral

Mimetite

Size

Cabinet; 54mm

Location in the Mine

First oxidation zone

Provenance

Ward's NSE

Collection

MGMH; 86706

Entry Number

Specimen; TSNB675

Associated Minerals

anglesite; arsentsumebite (?); gartrellite (?)

Description

Mimetite, both as a matrix component and as free-standing crystals, extensively replaced by arsenate minerals – green arsentsumebite (?) and yellow gartrellite (?) are likely candidates, but these have not been verified. Tiny aggregates of minute (< 0.1 mm), translucent red-brown crystals are present on the yellow gartrellite (?) and are as yet undetermined.


A crust of white anglesite (EDS verified; Frank Keutsch, Harvard University, 2025) is present on one of the pseudomorphed mimetites.


The specimen was acquired from Wards Natural Science Establishment. While there is no record of location in the mine the paragenesis is definitive for the first oxidation zone.