Davinciite

Davinciite is a very rare mineral of the eudialyte group,^[2][3] with the simplified formula Na₁₂K₃Ca₆Fe₃²⁺Zr₃(Si₂₆O₇₃OH)Cl₂.^[2][4] The formula given does not show the presence of cyclic silicate groups. The mineral was named after Leonardo da Vinci^[4] 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.^[3]

Davinciite
General
Category	Silicate mineral, Cyclosilicate
Formula	Na12K3Ca6Fe2+3Zr3(Si26O73OH)Cl2 (original form)
IMA symbol	Dvc[1]
Crystal system	Trigonal
Crystal class	Ditrigonal pyramidal (3m) H-M symbol: (3m)
Space group	R3m
Unit cell	a = 14.29, c = 30.03 [Å] (approximated), Z = 3
Identification
Colour	Dark lavender
Crystal habit	inclusions in rastsvetaevite
Cleavage	None
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	5
Luster	Vitreous
Streak	White
Diaphaneity	Transparent
Density	2.82 (measured), 2.85 (calculated; approximated)
Optical properties	Uniaxial (+)
Refractive index	nω=1.61, nε=1.61 (approximated)
Pleochroism	None
Ultraviolet fluorescence	No
Common impurities	Sr, Mn, Ti, H2O
References	[2][3]

Occurrence and association

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.^[3]

Notes on chemistry

Impurities in davinciite include strontium, manganese, titanium, with minor aluminium, barium, hafnium, and niobium. Some water is also present.^[3]

See also

• List of minerals
• List of minerals named after people