Spessartine

Spectrum Details

Modality

NIR

Category

mineral

Material Type

Nesosilicate

Sample ID

HS112.3B

Collection Locality

Haddon, Connecticut

Spectral Purity

1b2c3c4_ # HS112.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

Composition / XRD

None # XRF, EPMA, ICP(Trace), WChem COMPOSITION_TRACE:

Sample Description

Forms series with Almandine. "Spessartite 112B--Haddon, Conn. Mn3Al2(SiO4)3: Spessartite is less common than many garnets, occurring primarily in metamorphic rocks and granite pegmatites. The dominant features in the spectrum are the intense bands at 1.275 and 1.7 µ due to the presence of ferrous iron in eight-fold coordination, as discussed above. The visible spectrum falls off sharply to the blue producing a maximum near 0.8 µ. In the larger particle sizes this feature shows a shoulder near 0.9 µ, indicating the presence of Fe^3+. While the visible spectrum displays the very sharp feature at 0.41 µ characteristic of Mn^2+ absorption, the rest of its usually distinctive spectrum is degraded by the presence of absorptions by both Fe^3+ and Fe^2+. Together these 3 ions can account for the bands at 0.37, 0.43 µ, the broad general absorption centered near 0.55 µ, and the fall off to the blue." 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. IMAGE_OF_SAMPLE:

XRD Analysis

40 kV - 30 mA, 6.7-9.5 keV File: spes112.mdi References: Huebner's reference patterns Found: Garnet, minor quartz Comments: Garnet peaks are moderately sharp. Resolution of the alpha1-alpha2 components is not as good as might be expected from the sharpness, and slight shoulders extend toward larger d-spacings, suggesting that slight compositional zoning may be present. The cell dimension of the garnet is 11.65 Angstroms, consistent with a spessartine-rich garnet.

X Units

cm⁻¹

Y Units

Absorbance

Data Points

2,126