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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Joseph E. Taggart</dc:contributor>
  <dc:contributor>R. V. Gaines</dc:contributor>
  <dc:contributor>P. L .C. Grubb</dc:contributor>
  <dc:contributor>R. Kristiansen</dc:contributor>
  <dc:creator>Eugene E. Foord</dc:creator>
  <dc:date>1986</dc:date>
  <dc:description>&lt;p&gt;Zimbabweite (Na,K)&lt;sub&gt;2&lt;/sub&gt;PbAs&lt;sub&gt;4&lt;/sub&gt;(Ta,Nb,Ti)&lt;sub&gt;4&lt;/sub&gt;O&lt;sub&gt;18&lt;/sub&gt;, a new mineral with trivalent arsenic, has been recognized at St Anns mine, southeast of Miami, Karoi district, Zimbabwe, in kaolinized pegmatite and dump material.&lt;/p&gt;&lt;p&gt;The mineral is honey yellow-brown in large crystals, which are as much as 1 x 1 x 2 cm, and is clear pale yellow in thin fragments. Oxidation results in darkening of the color. There is one excellent cleavage, {010}. Zimbabweite has a Mohs hardness of 5 to 5.5, a white streak, adamantine luster, brittle fracture, is not magnetic, and does not fluoresce under either short wave or long wave ultraviolet light. d&lt;sub&gt;m&lt;/sub&gt; = 6.20(3) and d&lt;sub&gt;c&lt;/sub&gt; = 6.16 g/cm3. Optically, the mineral is biaxial (+), 2V&lt;sub&gt;Z&lt;/sub&gt; = about 80°. Mean reflectances in air for an {010} = X-Z cleavage plate are : 589 nm--16.6 %, 470 nm--17.7 %, 546 nm--17.1 %, 650 nm--16.4 %. The indices of refraction determined by immersion methods are all greater than 2.10. Optic axis dispersion is very strong with ν &amp;gt; r, a = Z, b = Y, and c = X. The mineral is very pale yelow and is moderately pleochroic and X = pale yellow brown, Y = light reddish brown, and Z =reddish brown.&lt;br&gt;&lt;/p&gt;&lt;p&gt;Zimbabweite is insoluble in common acids or bases. A chemical analysis yielded, in weight percent, Ta&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; 46.5, As&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; 26.5, PbO 15.0, Nb&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; 4.8, Na&lt;sub&gt;2&lt;/sub&gt;O 3.1, K&lt;sub&gt;2&lt;/sub&gt;O 1.5, TiO&lt;sub&gt;2&lt;/sub&gt; 1.4, BaO 0.4, UO&lt;sub&gt;2&lt;/sub&gt; 0.3, Bi&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3 &lt;/sub&gt;0.2, H&lt;sub&gt;2&lt;/sub&gt;O (total) 0.19, SnO&lt;sub&gt;2&lt;/sub&gt; 0.1, F 0.04, SrO 0.02, total 100.05. A calculated formula is :&lt;br&gt;(Na&lt;sub&gt;1.51&lt;/sub&gt;K&lt;sub&gt;0.48&lt;/sub&gt;Ba&lt;sub&gt;0.04&lt;/sub&gt;)&lt;sub&gt;Σ2.03&lt;/sub&gt;Pb&lt;sub&gt;1.01&lt;/sub&gt;(As&lt;sub&gt;4.03&lt;/sub&gt;Bi&lt;sub&gt;0.01&lt;/sub&gt;)&lt;sub&gt;Σ4.04&lt;/sub&gt;(Ta&lt;sub&gt;3.17&lt;/sub&gt;Nb&lt;sub&gt;0.55&lt;/sub&gt;Ti&lt;sub&gt;0.26&lt;/sub&gt;U&lt;sub&gt;0.02&lt;/sub&gt;Sn&lt;sub&gt;0.01&lt;/sub&gt;)&lt;sub&gt;Σ4.01&lt;/sub&gt;O&lt;sub&gt;18&lt;/sub&gt;.&lt;br&gt;&lt;/p&gt;&lt;p&gt;Zimbabweite is orthorhombic, space group is &lt;i&gt;Ccma&lt;/i&gt; or &lt;i&gt;Cc2a&lt;/i&gt;, with &lt;i&gt;a&lt;/i&gt; = 12.233(2)Å, &lt;i&gt;b&lt;/i&gt; = 15.292(2)Å, &lt;i&gt;c&lt;/i&gt; = 8.665(2)Å, V = 1621. 0(4) Å&lt;sub&gt;3&lt;/sub&gt;, with Z = 4. No structural relationship between zimbabweite and any other tantalate minerals is apparent.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.3406/bulmi.1986.7943</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Persee</dc:publisher>
  <dc:title>Zimbabweite, a new alkali-lead arsenic tantalate from St Anns mine, Karoi district, Zimbabwe</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>