zinnwaldite

{{Short description|Phyllosilicate mineral series in the mica group}}

{{Infobox mineral

| name = Zinnwaldite

| category = Phyllosilicate minerals, mica group

| boxwidth =

| boxbgcolor =

| image = Fluorapatite-Quartz-Topaz-gha5a.jpg

| imagesize = 260px

| caption = Fluorapatite with topaz on zinnwaldite and quartz

| formula = KLiFeAl(AlSi₃)O₁₀(OH,F)₂

| IMAsymbol = Znw{{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 =

| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = Cc (no. 9)

| unit cell = a = 5.29, b = 9.14
c = 10.09 [Å]; β = 100.83°

| color = Gray-brown, yellow-brown, pale violet, dark green, color zoning common

| habit = Well-formed short prismatic or tabular crystals, pseudohexagonal, in rosettes or fan-shaped groups; lamellar or scaly aggregates; disseminated.

| twinning = On composition plane {001}, twin axis [310]

| cleavage = Perfect basal {001}

| fracture = Uneven

| tenacity = Laminae °exible, elastic

| mohs = 3.5 - 4.0

| luster = Pearly to vitreous

| refractive = nα = 1.565 - 1.625 nβ = 1.605 - 1.675 nγ = 1.605 - 1.675

| opticalprop = Biaxial (-)

| birefringence = 0.040 - 0.050

| pleochroism = Distinct, X = colorless to yellow-brown; Y = gray-brown; Z = colorless to gray-brown

| 2V = 0 - 40°

| streak = White

| gravity = 2.9 - 3.1

| density =

| melt =

| fusibility =

| diagnostic =

| solubility =

| diaphaneity = Transparent to translucent

| references = [http://webmineral.com/data/Zinnwaldite.shtml Webmineral data]{{cite journal |last1=Rieder |first1=M. |last2=Hybler |first2=J. |last3=Smrcok |first3=L. |last4=Weiss |first4=Z. |journal=European Journal of Mineralogy |volume=8 |year=1996 |pages=1241–1248 |title=Refinement of the crystal structure of zinnwaldite 2M_1 |issue=6 |doi=10.1127/ejm/8/6/1241}}

}}

Zinnwaldite, KLiFeAl(AlSi₃)O₁₀(OH,F)₂, potassium lithium iron aluminium silicate hydroxide fluoride, is a silicate mineral in the mica group. The IMA status is as a series between siderophyllite (KFe₂Al(Al₂Si₂)O₁₀(F,OH)₂) and polylithionite (KLi₂AlSi₄O₁₀(F,OH)₂) and not considered a valid mineral species.