| Davinciite | |
| Category: | Silicate mineral, Cyclosilicate |
| Formula: | Na12K3Ca6Fe2+3Zr3(Si26O73OH)Cl2 (original form) |
| Imasymbol: | Dvc[1] |
| System: | Trigonal |
| Class: | Ditrigonal pyramidal (3m) H-M symbol: (3m) |
| Symmetry: | R3m |
| Unit Cell: | a = 14.29, c = 30.03 [Å] (approximated), Z = 3 |
| Colour: | Dark lavender |
| Habit: | inclusions in rastsvetaevite |
| Cleavage: | None |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Mohs: | 5 |
| Luster: | Vitreous |
| Streak: | White |
| Diaphaneity: | Transparent |
| Density: | 2.82 (measured), 2.85 (calculated; approximated) |
| Opticalprop: | Uniaxial (+) |
| Refractive: | nω=1.61, nε=1.61 (approximated) |
| Pleochroism: | None |
| Fluorescence: | No |
| Impurities: | Sr, Mn, Ti, H2O |
Davinciite is a very rare mineral of the eudialyte group,[2] with the simplified formula Na12K3Ca6Fe32+Zr3(Si26O73OH)Cl2.[3] [4] 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.
Davinciite was discovered in hyperagpaitic (highly alkaline) pegmatite at Mt. Rasvmuchorr, Khibiny massif, Kola Peninsula, Russia. Aegirine, delhayelite, nepheline, potassium feldspar, shcherbakovite, sodalite (silicates), djerfisherite, rasvumite (sulfides), nitrite, nacaphite, and villiaumite are associated minerals.
Impurities in davinciite include strontium, manganese, titanium, with minor aluminium, barium, hafnium, and niobium. Some water is also present.