hardystonite

{{Short description|Sorosilicate mineral}}

{{Infobox mineral

| name = Hardystonite

| category = Sorosilicates

| image = Hardystonite-Clinohedrite-Calcite-170573.jpg

| imagesize = 260px

| caption = Hardystonite is fluorescing blue in this Franklin Furnace specimen. Red is calcite, and green is willemite (size: 7.0 × 6.0 × 3.2 cm)

| formula = Ca₂ZnSi₂O₇

| IMAsymbol = Hdy{{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}}

| strunz = 9.BB.10

| dana = 55.4.2.2

| system = Tetragonal

| class = Scalenohedral ({{overline|4}}2m)
H-M symbol: ({{overline|4}} 2m)

| symmetry = P{{overline|4}}2₁m

| unit cell = a = 7.8287(16) Å
c = 5.0140(2) Å; Z = 2

| color = Light brownish white, pale greyish-white, very pale pink

| colour =

| habit = Massive granular

| twinning =

| cleavage = [001] good, [100] and [110] fair

| fracture =

| tenacity = Brittle

| mohs = 3–4

| luster = Vitreous, resinous, greasy, dull

| streak =

| diaphaneity = Transparent to translucent

| gravity = 3.396–3.443

| density =

| polish =

| opticalprop = Uniaxial (−)

| refractive = n_ω = 1.672 n_ε = 1.661

| birefringence =

| pleochroism =

| 2V =

| dispersion =

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| length fast/slow =

| fluorescence = Purple to violet blue in short wave ultraviolet light

| absorption =

| melt =

| fusibility =

| diagnostic =

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| other =

| alteration = Hydrothermal alteration to clinohedrite

| references = http://www.mindat.org/min-1818.html Mindathttp://www.webmineral.com/data/Hardystonite.shtml Webmineral data[http://rruff.geo.arizona.edu/doclib/hom/hardystonite.pdf Handbook of Mineralogy]

}}

Hardystonite is a rare calcium zinc silicate mineral first described from the Franklin, New Jersey, U.S. zinc deposits. It often contains lead, which was detrimental to the zinc smelting process, so it was not a useful ore mineral.{{Cite Q|Q58144929|author=Palache, Charles|author-link=Charles Palache}} Like many of the famous Franklin minerals, hardystonite responds to short wave ultraviolet (254 nm wavelength) light, emitting a fluorescence from dark purple to bright violet blue. In daylight, it is white to gray to light pink in color, sometimes with a vitreous or greasy luster. It is very rarely found as well formed crystals, and these are usually rectangular in appearance and rock-locked.Dunn, Pete J. Franklin and Sterling Hill, New Jersey: the world's most magnificent mineral deposits. Dr. Pete J. Dunn, 2004.

File:Hardystonite-Clinohedrite-Calcite-170572.jpg

Hardystonite has a chemical composition of Ca₂ZnSi₂O₇. It is frequently found with willemite (fluoresces green), calcite (fluoresces red), and clinohedrite (fluoresces orange). Hardystonite can be found altered to clinohedrite CaZn(SiO₄)·H₂O through direct hydrothermal alteration.

Other minerals often associated with hardystonite are franklinite, diopside, andradite garnet, and esperite (fluoresces yellow).

It was first described in 1899 by J.E. Wolff, when the New Jersey Zinc Company mines were located in what was called Franklin Furnace, in Hardyston Township, New Jersey.