TITLE: Psilomelane HS139 DESCRIPT
MINERAL_TYPE: Hydroxide (Mineral mixture)
MINERAL: Psilomelane (Romanechite)
COLLECTION_LOCALITY: Magdalena, New Mexico
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
"0-13. Psilomelane. Magdalena, N.M. (139B). "Psilomelane" is generally used as a field term for any poorly characterized massive ore of manganese. Much of the material originally cleared as psilomelane consists of mixtures of several different minerals, usually with pyrolusite (Palache et al., 1944). Psilomelane usually is of supergene origin, occurring typically as a weathering product of manganiferous carbonates or silicates. This particular sample has a black streak, and yields very little water (0.09%) when heated. Consequently, we conclude that it is composed in large part of pyrolusite. Its spectrum is opaque and spectrally featureless, due to the conduction band of MnO2 extending throughout this spectral range."
Sieve interval 74 - 250µm.
Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1971, Visible and near-infrared spectra of minerals and rocks: III. Oxides and hydroxides. Modern Geology, v. 2, p. 195-205.
"Many of the hard botryoidal masses formerly called psilomelane are now known to be a mixture of several manganese oxides of which romanechite is a major constituent. Some of the other minerals commonly present in the mixture are cryptomelane, KMn8,O16; manjiroite, (Na,K)Mn8O16.nH2O; and todorokite (Mn,Ca,Mg) Mn3O7.H2O."
Klein, C. and Hurlbut, C.S., Manual of Mineralogy 20th Edition, pp 317-318, 1985.
40 kV - 30 mA, 7.0-9.5 keV
File: psilm139.mdi (smear on qtz plate)
References: PDF2 #14-0627
Comments: All peaks are weak, most peaks broad, and the alpha1-alpha2 components are not resolved. The pattern has high background, probably due to Mn or Fe X-ray fluorescence. Within the range covered by the PDF2 data, all observed reflections were indexable as romanechite. There are some differences in intensity, however. The PDF2 lists additional reflections which were not observed in our poor pattern.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
LIB_SPECTRA: splib04a r 3989 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=