Brendelite was found on specimens from the dumps of the Güldener Falk mine near Schneeberg, Saxony, Germany. The new mineral shows monoclinic holohedral symmetry and forms idiomorphic crystals (
{ [`2]01}\{ \bar 201\}
, with additional forms of {001}, {010}, and {100}. The colour is black to dark brown, the streak is light brown and the lustre is vitreous to adamantine. The Mohs' hardness is
4\frac124\frac{1}{2}
. No cleavage was observed. Brendelite is biaxial negative, 2V = 70(5)° (from extinction curves), n
x=2.06, n
y=2.15 (calc.), n
Z=2.19 (from reflectivity measurements). Z is II to [010] and Y is
Bi1.27 Pb0.74 )S = 2.01 (Fe0.743 + Fe0.272 + )S = 1.01 [O2.00 (OH)1.00 )]S = 3.00 ·[(PO4 )0.95 (AsO4 )0.02 (VO4 )0.02 ]S = 0.99 \begin{gathered} Bi_{1.27} Pb_{0.74} )_{\Sigma = 2.01} (Fe_{0.74}^{3 + } Fe_{0.27}^{2 + } )_{\Sigma = 1.01} [O_{2.00} (OH)_{1.00} )]_{\Sigma = 3.00} \hfill \\ \cdot [(PO_4 )_{0.95} ({\rm A}sO_4 )_{0.02} (VO_4 )_{0.02} ]_{\Sigma = 0.99}\end{gathered}
and the simplified formula as derived from chemical analyses and crystal-structure investigation is (Bi,Pb)
2Fe
3+,2-O
2(OH)(PO
4). Brendelite is monoclinic with space group C2/
m,a=12.278(2)Å,
b=3.815(1)Å,
c=6.899(1) Å,
{ [`2]01}\{ \bar 201\}
, zusätzlich treten die Formen {001}, {010}, und {100} auf. Die äußeren Kennzeichen sind schwarze bis dunkelbraune Farbe, hellbrauner Strich und Glas- bis Diamantglanz. Die Mohs'sche Härte ist
4\frac124\frac{1}{2}
. Eine Spaltbarkeit wurde nicht beobachtet. Brendelit ist zweiachsig negativ, 2V = 70(5)° (aus Auslöschungskurven), n
x = 2,06, ny = 2,15 (ber.), n
Z = 2,19 (aus Reflexionsmessungen). Z ist II [010] und Y ist
Bi1.27 Pb0.74 )S = 2.01 (Fe0.743 + Fe0.272 + )S = 1.01 [O2.00 (OH)1.00 )]S = 3.00 ·[(PO4 )0.95 (AsO4 )0.02 (VO4 )0.02 ]S = 0.99 \begin{gathered} Bi_{1.27} Pb_{0.74} )_{\Sigma = 2.01} (Fe_{0.74}^{3 + } Fe_{0.27}^{2 + } )_{\Sigma = 1.01} [O_{2.00} (OH)_{1.00} )]_{\Sigma = 3.00} \hfill \\ \cdot [(PO_4 )_{0.95} ({\rm A}sO_4 )_{0.02} (VO_4 )_{0.02} ]_{\Sigma = 0.99}\end{gathered}
aus chemischer Analyse und Kristallstrukturuntersuchung ergibt sich die vereinfachte Formel (Bi,Pb)
). Brendelit ist monoklin, Raumgruppe
= 111,14(1)°, V=301,4(1)Å, und Z=2.