Using the Alunite Shift as an Indicator in
1 Canal Street ◊ Unit B1
Lawrence, MA 01840 USA
Tel: 978 687-1833 ◊ Fax: 978 945-0372
Copyright © 2012 Spectral Evolution, Inc
Alunite characteristics can provide a good indication of gold ore
potential in a high sulfidation epithermal system. Alunite is a
potassium sulfate mineral that forms in hydrothermal systems.
Sulfates such as alunite and jarosite are common in hydrothermal
environments and have distinctive NIR spectra. Alunites have the
potential to delineate zoning based on chemical and temperature
changes in the hydrothermal system.
By measuring the shift in alunite from potassium rich (K-alunite) to
sodic (Na-alunite) a geologist can have a better understanding of the
mineral alteration and can use this data to vector to mineralization.
The shift is typically seen at the 1480-1490nm wavelength in an NIR
spectra and is thought to be a record of the mineralizing effect of
magmatic and meteoric fluids.
The oreXpress is a field portable NIR spectrometer that provides
mineral identification and analysis for in situ measurements.
Lightweight and rugged, the oreXpress is used in the field with two
lithium-ion batteries for 6-8 hours of scanning outcrops, pits, and
benches. The system has no moving optical parts - solid state
photodiode arrays prevent accidental breakage of misalignment.
With our mineral contact probe, a geologist can scan a large area and
create a mineral map. With the optional EZ-ID mineral identification
software of more than 600 minerals and 1600 spectra, identifying
typical minerals in hydrothermal systems like kaolinite, jarosite,
dickite, pyrophyllite, and zunyite, is fast and accurate.
With the oreXpress and EZ-ID, the return-on-investment can occur
very quickly by eliminating drill holes in unprofitable locations and
concentrating on spots that are indicative of profitable mineral
Alunite sample. Alunites are important pathfinder
minerals in both gold and copper systems.
Close-up of two alunite samples from core showing the
shift from potassium rich alunite (blue) to sodium rich
EZ-ID mineral identification software can be usewd to
identify alunite and other associated minerals
including jarosite, kaolinitie, dickite, pyrophyllite and
zunyite. With two libraries of 600 minerals and 1600
spectra, EZ-ID matches the high resolution scan of
your target sample to a known library spectra.