Mineral: Bournonite
Locality: Víboras Mine, Machacamarca, Machacamarca District, Cornelio Saavedra Province, Potosí Department, Bolivia
Dimensions: 16 x 16 x 14.5 cm / main crystal: 10.8 cm.

Description: Mass: 4710 g MIM number: 2269 Large cluster of bright crystals in subparallel formation. These very well-formed crystals resemble cogwheels (which is the characteristic twinning of this species) giving this sample the appearance of a gearbox, hence its nickname, "The Gearbox". It is remarkable that such a large plate could be recovered intact, knowing that bournonite is a very fragile mineral. This is one of the largest and best groups of this mineral found in Bolivia. Photographer: AINU / Augustin de Valence; Publication: "Rocks & Minerals: Vol. 98, No.6 Nov/Dec 2023"

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