TITLE: Natrojarosite + Gypsum + Illite BRCM-1
MATERIAL TYPE: MINERAL
SAMPLE ID: BRCM-1
MINERAL TYPE: Intimate mixture
FORMULA:
COLLECTION LOCALITY: Lower, northeastern slopes of Big Rock Candy Mountain,
Sevier and Piute Counties, Utah
COLLECTION LOCALITY LAT/LONG: 38º 30’ 42.32” N, 112º 15’
44.41” W
ORIGINAL DONOR: Barnaby W. Rockwell
CURRENT SAMPLE LOCATION: USGS Denver, CO
ULTIMATE SAMPLE LOCATION: USGS Denver, CO
SAMPLE DESCRIPTION:
Weathered andesitic lava flows from pyritic, propylitically altered feeder zone of hydrothermal system formed at ~21 Ma (Miocene). Fine-grained, yellowish jarositic coatings on light grey, thoroughly altered rock.
XRD ANALYSIS:
Major (>25%): albite
Minor (5%-25%): quartz, gypsum, natrojarosite, illite, muscovite
Trace (<5%): pyrite, dolomite
COMPOSITIONAL ANALYSIS TYPE: EM(WDS) # XRF,
EM(WDS), ICP(Trace), WChem
Compound/Element |
Composition weight % |
|---|---|
|
SiO2 |
|
|
TiO2 |
|
|
Al2O3 |
|
|
FeO |
|
|
MnO |
|
|
MgO |
|
|
CaO |
|
|
Na2O |
|
|
K2O |
|
| Total |
|
|
O=Cl,F,S |
|
| New Total |
|
COMPOSITION DISCUSSION:
MICROSCOPIC EXAMINATION:
Scanning Electron Microscope (SEM) images found crystals of natrojarosite ranging in size from 2-5 microns in diameter, large crystals of gypsum of 10 microns and larger, and amorphous coatings of iron oxides and hydroxides around grains of other minerals.
WAVELENGTH INTERVALS OF ABSORPTION FEATURES USED IN SPECTRAL ANALYSIS:
| Absorption |
Left
continuum endpoint |
Right
continuum endpoint |
||
|---|---|---|---|---|
| 1 |
2.115 |
2.145 |
2.305 |
2.335 |
| 2 |
1.495 |
1.525 |
1.555 |
1.585 |
| 3 |
1.690 |
1.720 |
1.755 |
1.785 |
| 4 |
0.706 |
0.738 |
1.286 |
1.320 |
|
5 (W) |
0.406 |
0.426 |
0.460 |
0.480 |
SPECTRAL REGION USED FOR CURVE SHAPE COMPETITION: 1.4 - 2.5 µm, Tetracorder group 2
SPECTROSCOPIC DISCUSSION:
This mineral mixture has been mapped with AVIRIS data in pyritic tailings at mill sites and waste rock at mine sites.
USGS SPECTRAL LIBRARY LOCATION AND SPECTRAL RANGE: sprlf01a r 367 0.35-2.50µm
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