Almandine

Spectrum Details

Modality

NIR

Category

mineral

Material Type

Nesosilicate

Sample ID

HS114.1B, HS114.2B, HS114.3B, HS114.4B, HS114.6

Collection Locality

Warren County, New York

Spectral Purity

1b2_3_4_ # HS114.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns SPECTRAL_PURITY: 1b2_3_4_ # HS114.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns SPECTRAL_PURITY: 1b2b3b4_ # HS114.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns SPECTRAL_PURITY: 1b2_3_4_ # HS114.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns SPECTRAL_PURITY: 1b2_3_4_ # HS114.6 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

Composition / XRD

EM # XRF, EPMA, ICP(Trace), WChem

Sample Description

Forms series with Pyrope and with Spessartine. "This is a common garnet of schists and gneisses and also occurs in intermediate to acidic igneous rocks. It is the most widespread variety of garnet found as a detrital mineral in sedimentary rocks. Again, this spectrum is dominated by the intense absorption at 1.28 &#181m; and 1.7 &#181m; due to the ferrous iron in eight-fold coordination. Also, there is a rapid fall off to the blue caused by both ferrous and ferric ion absorptions. The well defined band at 0.7 &#181m; confirms the presence of Fe^+3 substituted for Al^+3, and the suggestion of a band near 0.85&#181m; in the smallest particle size is consistent with this - even though the combination of the visible and near-infrared intense absorptions provide a well-resolved maximum near 0.85 µm, especially in the larger particle size samples. The visible spectrum shows features at 0.37, 0.43, 0.51, and 0.57 &#181m;, which is quite similar to the spectrum of spessartine, with the exception of the very sharp 0.41 &#181m; Mn^+2 band, which is absent." Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1973, Visible and near-infrared spectra of minerals and rocks: VI. Additional silicates. Modern Geology, v. 4, p. 85-106. Grain size fractions are indicated by the extension after the sample number: .1B = IMAGE_OF_SAMPLE:

XRD Analysis

40 kV - 30 mA, 7.3 -9.5 keV File: alma114.out, *_mdi (smear mount on quartz plate) References: Borg and Smith (1969), JCPDS #9-427, DHZ, v. 1a (1982), Huebner's reference patterns Found: Garnet; very weak un indexed reflection at 2.29 Angstroms Comment: Very sharp reflections indicate excellent crystallinity and suggest compositional homogeneity. Garnet ao=11.51+/-3 Angstroms, consistent with almandine composition (at 11.526 Angstroms). Unusual rise in background centered about 42 degrees 2 theta. J.S. Huebner, J. Pickrell, T. Schaefer, written communication 1994

X Units

cm⁻¹

Y Units

Absorbance

Data Points

2,126