avogadrite

{{Short description|Halide mineral}}

{{Infobox mineral

| name = Avogadrite

| category = Halide mineral

| image = Ferruccite, Avogadrite - Vesuvius, Italia.jpg

| caption = Ferruccite (white) on avogadrite (yellow-brownish), picture size: 5 mm

| formula = (K,Cs)BF₄

|IMAsymbol=Avg{{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 = 3.CA.10

| system = Orthorhombic

| class = Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)

| symmetry = Pnma

| unit cell = a = 8.6588, b = 5.48
c = 7.0299 [Å]; Z = 4

| color = Colorless to white, yellowish to reddish

| habit = Tabular to platy octagonal crystals, tiny crystals, elongate

| twinning =

| cleavage =

| fracture =

| mohs =

| luster = Vitreous, greasy

| refractive = n_α = 1.3239, n_β = 1.3245, n_γ = 1.3247

| opticalprop = Biaxial (-)

| birefringence = δ = 0.001

| 2V = 75°(meas), 58° (calc)

| pleochroism =

| streak =

| gravity = 2.9

| density =

| melt =

| fusibility =

| diagnostic =

| solubility =

| diaphaneity = Translucent

| other = Bitter taste

| references = {{cite web | url = http://www.handbookofmineralogy.org/pdfs/AVOGADRITE.pdf | publisher = The Mineralogical Society of America | title = Handbook of Mineralogy: Avogadrite | access-date = 2010-01-09 | archive-date = 2012-02-18 | archive-url = https://web.archive.org/web/20120218224538/http://www.handbookofmineralogy.org/pdfs/AVOGADRITE.pdf | url-status = dead }}[http://www.mindat.org/min-438.html Avogadrite on Mindat.org][http://www.webmineral.com/data/Avogadrite.shtml#.VnoRFrY4HRY Avogadrite data on Webmin]

}}

Avogadrite ((K,Cs)BF₄) is a potassium-caesium tetrafluoroborate in the halide class. Avogadrite crystallizes in the orthorhombic system (space group Pnma) with cell parameters a 8.66 Å, b 5.48 Å and c Å 7.03.