Davinciite

{{infobox mineral

| name = Davinciite

| category = Silicate mineral, Cyclosilicate

| image =

| imagesize =

| alt =

| caption =

| formula = Na₁₂K₃Ca₆Fe²⁺₃Zr₃(Si₂₆O₇₃OH)Cl₂ (original form)

| IMAsymbol = Dvc{{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 =

| dana =

| system = Trigonal

| class = Ditrigonal pyramidal (3m)
H-M symbol: (3m)

| symmetry = R3m

| unit cell = a = 14.29, c = 30.03 [Å] (approximated), Z = 3

| color =

| colour = Dark lavender

| habit = inclusions in rastsvetaevite

| twinning =

| cleavage = None

| fracture = Conchoidal

| tenacity = Brittle

| mohs = 5

| luster = Vitreous

| streak = White

| diaphaneity = Transparent

| gravity =

| density = 2.82 (measured), 2.85 (calculated; approximated)

| polish =

| opticalprop = Uniaxial (+)

| refractive = nω=1.61, nε=1.61 (approximated)

| birefringence =

| pleochroism = None

| 2V =

| dispersion =

| extinction =

| length fast/slow =

| fluorescence = No

| absorption =

| melt =

| fusibility =

| diagnostic =

| solubility =

| impurities = Sr, Mn, Ti, H₂O

| alteration =

| other =

| references =

}}

Davinciite is a very rare mineral of the eudialyte group,{{cite journal| last1= Khomyakov| first1= A.P.| first2= G.N. | last2= Nechelyustov| first3= R.K. | last3= Rastsvetaeva | first4= K.A. | last4= Rozenberg| year=2012|title= Davinciite, Na₁₂K₃Ca₆Fe²⁺₃Zr₃(Si₂₆O₇₃OH)Cl₂, a new K, Na-ordered mineral of the eudialyte group from the Khibiny alkaline massif, Kola Peninsula, Russia| journal= Zap. Ross. Mineral. Obshch.| volume= 141| number=2| pages= 10–21 |language= Russian, English| doi= 10.1134/S1075701513070076| s2cid= 97821896}} with the simplified formula Na₁₂K₃Ca₆Fe₃²⁺Zr₃(Si₂₆O₇₃OH)Cl₂.{{cite web|url=http://www.mindat.org/min-42815.html |title=Davinciite: Davinciite mineral information and data |website=Mindat.org |accessdate=2016-03-08}}{{cite web| url= http://www.handbookofmineralogy.org/pdfs/davinciite.pdf| title= Davinciite | website= HandbookofMineralogy.org| accessdate= March 1, 2016}} The formula given does not show the presence of cyclic silicate groups. The mineral was named after Leonardo da Vinci to refer to the atypical geometrical forms he tended to use, compared by the authors of the mineral description to the atypical (not ideally centrosymmetrical) geometry of the Davinciite structure. The other quite atypical feature of Davinciite is its lavender colour, while the typical eudialyte is rather pink or red.