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Makarochkinite,  [VII] (Ca 1.64 Na 0.25 Mn 0.11 ) [VI] (Fe 2+  3.56 Fe 3+  1.46 Ti 0.61 Mg 0.25 Mn 0.02 Nb 0.038 Ta 0.007 ) [IV] (Si 4.48 Be 0.91 Al 0.54 Fe 0.07 O 18 )O 2  (end-member Ca 2 Fe 4  2+ Fe 3+ TiSi 4 BeAlO 20 ) from electron-microprobe data, Mössbauer spectroscopy, and single-crystal structure refinement, occurs in a granitic pegmatite near Lake Ishkul', Il'men Mountains (Southern Urals), Il'men State Reserve, Chelyabinsk Oblast', Russia. Associated minerals include danalite, phenakite, titanite, potassian calcic amphibole (ferro-edenite and hastingsite), biotite, ilmenite, magnetite, ferrocolumbite, fergusonite-(Y), and samarskite-(Y). Makarochkinite forms equant masses 5.50 mm across, black in hand specimen; luster vitreous; it is opaque except in slivers &lt;1 μm thick. It is brittle; Moh's hardness 5.5.6, and has no discernable cleavage; fracture is uneven. Twinning is absent. The measured density is 3.93(1) g/cm 3 ; calculated density 3.933 g/cm 3 . It is optically biaxial, α = 1.835 ± 0.014 and γ = 1.865 ± 0.015 from reß ectance data, pleochroism marked: X = greenish brown, Y = yellowish brown, Z = reddish brown; Y ≤ X &lt; Z. Single-crystal X-ray diffraction gives triclinic symmetry, space group P1̅ . , Z = 2, wR(F 2 ) (all) = 0.096 for 6497 reß ections, a = 10.355(2), b = 10.751(3), and c = 8.873(2) Å, α = 105.707(8), β = 96.227(6), γ = 124.861(6)°, V = 735.7(3) Å 3 . The eight strongest lines in the powder pattern [d-spacing (Å),(I),(hkl)] are 7.997(57)(100), 4.779(29)(011), 3.120(32)(012), 2.924(69)(01̅3), 2.676(77)(2̅03), 2.530(100)(2̅1̅3), 2.410(28)(22̅3), 2.075(39)(41̅1).

american mineralogist

Makarochkinite, Ca 2 Fe 4  2+ Fe 3+ TiSi 4 BeAlO 20 , a new beryllosilicate member of the aenigmatite-sapphirine-surinamite group from the Ilʼmen Mountains (southern Urals), Russia