Franckeite

{{infobox mineral

| name = Franckeite

| category = Sulfosalt mineral

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| image = Franckeite-119411.jpg

| imagesize = 260px

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| caption = Franckeite var. Potosíite, San José Mine, Cercado Province Bolivia. Field of view about 10{{nbsp}}mm.

| formula = (Pb,Sn²⁺)₆Fe²⁺Sn₂Sb₂S₁₄

| IMAsymbol = Fke{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| molweight =

| strunz = 2.HF.25b

| dana = 03.01.04.02

| system = Triclinic

| class = Pinacoidal ({{overline|1}})
(same H-M symbol)

| symmetry = P{{overline|1}}

| color = Grayish black

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| habit = Typically in spherical, rosette aggregates of thin plates; commonly massive, radiated, or foliated

| twinning = Complex

| cleavage = {010}, perfect

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| tenacity = Flexible, inelastic; slightly malleable

| mohs = 2.5 – 3

| luster = Metallic

| streak = Grayish black

| diaphaneity = Opaque

| gravity = 5.88 – 5.92

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| pleochroism = Weak

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| references = http://rruff.geo.arizona.edu/doclib/hom/franckeite.pdf Handbook of Mineralogyhttp://www.mindat.org/min-1592.html Mindat with location datahttp://webmineral.com/data/Franckeite.shtml Webmineral data

}}

Franckeite, chemical formula Pb₅Sn₃Sb₂S₁₄, belongs to a family of complex sulfide minerals. Franckeite is a sulfosalt. It is closely related to cylindrite.

It was first described in 1893 for an occurrence in Chocaya, Potosí Department, Bolivia. It is named after the mining engineers, Carl and Ernest Francke. It can be found in Bolivia at Poopó in Oruro and at Las Aminas, southeast of Chocaya, in Potosi. Franckeite has an average density of 5.7 and can be both grayish black, blackish gray in color.

It occurs in hydrothermal silver-tin deposits in Bolivia and in contact metamorphosed limestone deposit in the Kalkar quarry in California. It occurs with cylindrite, teallite, plagionite, zinkenite, cassiterite, wurtzite, pyrrhotite,

marcasite, arsenopyrite, galena, pyrite, sphalerite, siderite and stannite.