Identifying Feldspars with a Field Spectrometer
 First in Full Range PDA Spectrometer, Spectroradiometer and Spectrophotometer Systems
1 Canal Street  ◊  Unit B1
Lawrence, MA 01840  USA
Tel: 978 687-1833  ◊  Fax: 978 945-0372

Copyright © 2012 Spectral Evolution, Inc
Feldspar minerals are found in igneous, metamorphic and
sedimentary rocks. Feldspars are used in industry for their aluminum
and alkali content and can appear as plagioclase feldspars or K-
feldspars or alkali feldspars. Plagioclase feldspars include:
  • Albite—Sodium aluminum silicate
  • Oligoclase—Sodium calcium aluminum silicate
  • Andesine—Sodium calcium aluminum silicate
  • Labradorite—Calcium sodium aluminum silicate
  • Bytownite—Calcium sodium aluminum silicate
  • Anorthite—Calcium aluminum silicate
While K-feldspars or alkali feldspars include:
  • Microcline—Potassium aluminum silicate
  • Sanidine—Potassium sodium aluminum silicate
  • Orthoclase—Potassium aluminum silicate

Industrial uses include glass for drinking, glass for protection, glass
wool for insulation,  ceramics including tile and tableware, fillers and
extenders in paint, plastics, and rubber, as well as other uses.

The plagioclase feldspars can be identified by Fe2+ absorption
feature between 1100 and 1300nm. The K-feldspars typically show
Fe3+ absorption bands at 860nm with a steep absorption edge near
600nm. Water absorption features may also occur for both groups at
1.4nm and 1.9nm.

The oreXpress high resolution/high sensitivity field spectrometer
can identify minerals. Used with EZ-ID mineral identification software
it matches your target minerals against known library samples for fast
identification. Samples for the plagioclase and K-feldspar minerals
are included in the libraries. EZ-ID allows you to create match regions
to focus on specific absorption features for unmixing multiple
minerals in a sample.

The oreXpress delivers full range UV/VIS/NIR/SWIR capabilities from
350-2500nm, is lightweight (under 7 lbs/3.5kg), rugged and includes
integral auto-exposure, auto-shutter, and auto-dark correction for on-
touch operation. An optional GETAC handheld microcomputer
includes a digital camera, GPS and voice notes—all data that can be  
tagged to your spectra. Use the oreXpress with our 10mm spot size
contact probe or our 3mm Miniprobe  or in the lab with our benchtop
probe with sample compactor.

In addition, our DARWin SP Data Acquisition software saves all scans
as ASCII files for use (without pre-processing) with third party
software such as the Spectral Geologist (TSG)  Version 8  and 3D
mapping and mining programs.
 First in Full Range PDA Spectrometer, Spectroradiometer and Spectrophotometer Systems
EZ-ID mineral identification software matches your samples against two libraries of
more than 600 mineral spectra including major plagioclase and k-feldspars. This
screen shot showes a sample of anorthite in the EZ-ID library.