jacobsite


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jacobsite

[′jā·kəb‚zīt]
(mineralogy)
MnFe2O4 A black magnetic mineral composed of an oxide of manganese and iron; a member of the magnetite series.
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SAED intensity profile, plotted as a function of [d.sup.-1] ([nm.sup.-1]), of the sample Mn25 presents the typical peaks of both maghemite and jacobsite [28] and the presence of manganosite and pyrolusite influences the symmetry of the peaks at 4.9 [nm.sup.-1] and 6.6 [nm.sup.-1] [28].
When the manganese concentration is further increased (sample Mn50), SAED intensity profile evidences the formation of structures strongly oriented and characterized by typical features of the jacobsite [28].
Dongri Buzurg Pyrolusite, Psilomelane, Jacobsite, Hematite, Goethite, Feldspar and Quartz 5.
Associated minerals are: jacobsite, kutnohorite, barite, tephroite and spessartine.
The composition of larger lobate grains shows their pertinence to titaniferous magnetite with a higher content of ulvospinel molecule ([Fe.sub.2]Ti[O.sub.4]) and low contents of Mn, Mg, Al, thus forming very low proportions of jacobsite, magnesioferrite, and hercynite, respectively, and sometimes V.
Helga and Horst Geuer (Am Sonnenhang 39, 53639 Konigswinter, Germany) had their usual excellent selection of specimens from Eifel and Lengenbach, the former including brenkite, calciobetafite, cuspidine, jacobsite, jasmundite, nickenichite, perrierite and srebrodolskite, and Lengenbach being represented by some early material from the Novacki Institute, which was also the source of some excellent specimens of marrite, rathite, seligmannite, trechmannite and imhofite, together with a small number of lengenbachite specimens of typical bladed form.