Andradite

Spectrum Details

Modality

FTIR

Category

mineral

Material Type

Nesosilicate

Sample ID

GDS12

Collection Locality

Esmerald Co., Nevada

Spectral Purity

1c2c3c4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

Composition / XRD

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

Sample Description

Forms series with Grossular and with Schorlomite. Sample is ground and sieved to less than 250 µm. Compare with other Andradite samples in library because spectral differences do exist between samples. Spectral features near 2.3 µm indicate trace spectral contamination. From the analyses below and the band position and shape, this appears to be calcite. Roger N. Clark IMAGE_OF_SAMPLE:

XRD Analysis

40 kV - 30 mA, 7.3-9.5 keV File: angds12.out, *.mdi References: Huebner's reference patterns Found: Garnet, probable clinopyroxene and alkali feldspar (two?) Comment: Difficult pattern to decipher. Four garnet compositions are resolved; the dominant garnet has ao=11.87 Angstroms, consistent with grossular-rich garnet. Other garnet compositions have larger cell dimensions (to ao=11.98 Angstroms), indicating andradite or uvarovite component. Based on brown color, the minor garnet compositions are andradite-rich. Many weak to very weak reflections are best described as a clinopyroxene (augite, not hedenbergite) and alkali feldspar (microcline + low albite). Optics are consistent; isotropic garnet, a low-birefringence phase with about 1.53 refractive index, and a moderate birefringence phase with about 1.69 refractive index.

X Units

cm⁻¹

Y Units

Absorbance

Data Points

1,801