The rare phosphate—nevadaite has been found at Kara-Chagyr (Batken region, Kyrgyzstan) in a zone of alteration of vanadium
bearing “black shales”. It occurs as blue crusts of spherulitic aggregates of tiny tabular crystals (0.1–10 μm). It is associated
with metahewettite, hummerite, carnotite, minyulite, fluellite, crandallite, variscite, and woodhouseite. Optical properties:
n = 1.542–1.555,
D
meas (for aggregates) = 2.58(1) g/cm
3,
D
calc = 2.582 g/cm
3. The most intense X-ray powder reflections are as follows: [
d/
n, Å, (
I
meas), (
hkl)]: 9.54 (80) (020), 6.03 (100) (200), 5.61 (100) (130), 3.91 (60) (310), 3.41 (80) (041), 2.982 (100) (241), 2.804 (60) (331),
2.672 (70) (061), 1.845 (60) (352) 1.507 (70) (243). Calculated cell dimensions are:
a = 12.072(10) Å,
b = 18.958(15) Å,
c = 4.969(5) Å, α = β = γ = 90°,
V = 1137.2 Å
3. Electron microprobe analyses gives (wt %): (observed (average of 8 analyses); (calculated for 22H
2O)): P
2O
5 34.69 (31.85), SiO
2 0.25 (0.24), Al
2O
3 25.61 (23.50), V
2O 5.58 (5.13), Fe
2O
3 0.48 (0.46), MnO 0.03 (0.03), CuO 10.79 (9.90), ZnO 0.69 (0.65), CaO 0.18 (0.15), MgO 0.17 (0.17), K
2O 0.08 (0.08), F 7.40 (6.79), H
2O 17.16 (by diff.) (23.90), −F
2 =O
$
\bar 3
$
\bar 3
.11 (
$
\bar 2
$
\bar 2
.86), total 100.00 (100.00).The crystal-chemical formula of the mineral is (Cu
2.2+2□
2.03V
1.21+3Al
0.15Zn
0.14Fe
0.10Mg
0.07Ca
0.05K
0.03Mn
0.01)
6.00(Al
8.00(P
7.93Si
0.07O
32)F
6.32(OH)
2.98 · 22(H
2O) for the ideal number of water molecules. Nevadaite from Kara-Chagyr differs from that from the type locality, Gold Quarry
(Nev., USA), by its lower Al content. The IR-spectrum, and microphotographs of nevadaite and associated minerals are given.
Original Russian Text © V.Y. Karpenko, L.A. Pautov, A.A. Agakhanov, 2009, published in Zapiski RMO (Proceedings of the Russian
Mineralogical Society), 2009, Pt. CXXXVII, No. 1, pp. 83–90.
The article was translated by the authors.