Field Identification of Carbonate Minerals with the oreXpress™ UV-VIS-NIR Spectrometer (350–2500 nm)

Introduction to Carbonates and Their Spectral Features
Carbonate minerals form when carbonate ions (CO₃²⁻) bond with metal cations to produce distinctive mineral groups such as calcite, dolomite, and aragonite. Within these groups there are important exploration minerals, including rhodochrosite, azurite, malachite, cerussite, magnesite, smithsonite, siderite, strontianite, and witherite. These minerals are commonly found in a variety of geological environments and can be key indicators of ore-forming processes. In the shortwave infrared (SWIR) spectral region, carbonates exhibit strong diagnostic absorption features between 2290–2350 nm caused by carbonate ion vibrational overtones. Subtle shifts in these features can be used for mineral discrimination; for example, dolomite has a primary absorption near 2325 nm, while calcite absorbs closer to 2340 nm, with calcite features typically occurring at slightly longer wavelengths.

oreXpress and EZ-ID™ for Carbonate Identification
The oreXpress field spectrometer, with full UV/VIS/NIR range from 350–2500 nm, combined with EZ-ID mineral identification software, offers a fast and non-destructive way to identify carbonate minerals in the field or core shack. EZ-ID matches unknown spectra against an extensive library of verified mineral samples, enabling confident identification even when minerals appear visually similar. This capability is particularly valuable for differentiating calcite from dolomite, which can be challenging in hand specimen but are clearly separated by their SWIR absorption positions. With on-site results available immediately, exploration teams can make informed decisions on sampling, mapping, and drilling without the delays associated with laboratory analysis.

Field and Core Logging Advantages
The oreXpress delivers rapid scanning that allows geologists to cover more ground in less time while collecting highly accurate data for improved geological interpretation. By quickly identifying carbonate-rich zones, alteration patterns, and mineralized targets, exploration programs can optimize drilling plans. In the core shack, the oreXpress ensures correct identification, reducing assay costs and preserving the quality of logging data. Rugged and lightweight, the instrument is designed for demanding field conditions and requires no sample preparation. A handheld tablet with a digital camera, and GPS allows spectra to be tagged with images, coordinates, and notes for complete field documentation.

Instrument Options, Data Integration, and Conclusion
For applications requiring higher resolution, the oreXplorer offers enhanced spectral resolution, while the oreXpert provides the highest resolution available in a field portable spectrometer. All models operate with DARWin™ Data Acquisition software, which saves spectra as ASCII files for direct use with third-party geological mapping and modeling software. By utilizing the precise SWIR absorption features of carbonates, the oreXpress and EZ-ID streamline mineral identification workflows, improve exploration efficiency, and deliver immediate, actionable results in the field. This approach allows geologists to make confident, data-driven decisions that reduce costs and accelerate the path from discovery to resource evaluation.