• journal_title：American Mineralogist
• Contributor：Radek Škoda ; Jan Cempírek ; Jan Filip ; Milan Novák ; František Veselovský ; Radim Čtvrtlík
• Publisher：Mineralogical Society of America
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.2138/am.2012.3936
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：97
• issue：5-6
• firstpage：983
• section：Articles

Allanite-(Nd), ideally CaNdAl₂Fe²⁺(SiO₄)(Si₂O₇)O(OH), the Nd-analog of allanite-(Ce), occurs in the Åskagen pegmatite, central Sweden. It forms fine-grained aggregates within altered thalénite-(Y). The other associated minerals include: iimoriite-(Y), keiviite-(Y), allanite-(Y), and tengerite-(Y). Allanite-(Nd) is biaxial (−); with refractive indices α = 1.723(5), β = 1.754(7), γ = 1.772(5), and measured 2V = 82°(±3°). Larger fragments of allanite-(Nd) are moderately pleochroic (α = pale grayish-brown, γ = grayish-brown); small fragments are colorless. Allanite-(Nd) is monoclinic, space group P2₁/m, with the following unit-cell parameters: a = 8.8897(5), b = 5.7308(2), c = 10.1010(6) Å, β = 115.166(7)°, V = 465.75(4) ų, Z = 2. The strongest five peaks from the X-ray powder diffraction patterns [d (Å)(I)(hkl)] are: 3.51(46)(2̄11), 2.89(100)(1̄13), 2.87(45)(020), 2.70(60)(120), 2.61(60)(3̄11). Allanite-(Nd) has a density of 3.98 g/cm³, vitreous luster, grayish-brown streak, and the Mohs hardness is ca. 6. It is brittle, with imperfect cleavage, and conchoidal fracture. The Mössbauer spectroscopy revealed Fe³⁺/Fe_tot ratio of 0.27 in the type sample. The refined empirical formula of the crystal used for the structure determination is:

The allanite-(Nd) was approved by CNMNC (IMA 2010-060).