A geology index — 0 compatible sensors — Last revised June 1, 2025
Phengitic
Phengitic
A geological spectral index designed for mineral exploration, particularly for identifying iron-related geological features. Commonly used with ASTER satellite data for geological mapping and alteration detection.
Used in mineral exploration.
When to use
- Mineral exploration target identification in arid and bare-ground regions
- Hydrothermal alteration zone mapping
- Lithological unit discrimination
- Iron oxide and clay mineral mapping
- Pre-field reconnaissance for geological surveys
- Geology
- Metal - Iron
Limitations
- Vegetation cover masks underlying mineral signatures — works best on bare ground
- Atmospheric water vapour absorbs in similar SWIR regions, requiring correction
- Particle size and mineral mixtures produce non-linear spectral mixing
- Should be combined with field validation — single-index identification is unreliable
- Different mineral assemblages can produce similar spectral signatures
- Requires sensors with SWIR bands — not available on all platforms
General Formula
Sensor-Specific Formulas
Most-used sensors — click to show code below
| Sensor | Provider | Formula | Band Mapping |
|---|
Code Examples
phengitic_generic.py
Phengitic vs other geology indices
| Index | Name | How it differs |
|---|---|---|
| AKP | Alunite/Kaolinite/Pyrophylite Index | Alternative geology index — different band combination |
| ALT | Alteration Index | Alternative geology index — different band combination |
| AMP | Amphibole Index | Alternative geology index — different band combination |
| Clay | Clay Index | Alternative geology index — different band combination |
Related Geology Indices
References
Hewson
Rob D. et al. (2001)
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