Abstract

MOSQUERA-RIVERA, Juan Esteban et al. Petrological characterization of variscite mineralization in Iza, Boyacá: First report in the Colombian Andes. Bol. geol. [online]. 2025, vol.47, n.3, pp.55-75.  Epub Nov 10, 2025. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v47n3-2025003.

The minerals of the variscite group constitute a rare family, known for their cyan-green hue, highly valued in jewellery, and their archaeological importance as ornamental gemstones in ancient artifacts and ornaments made in different parts of the world, used as a source of exchange and trade in prehistoric Europe. These belong mainly to the subclass of phosphates, but also to arsenates, vanadates, and selenates. In this study we characterized petrologically six samples of variscite found as mineralizations within arenites towards the top of the Guadalupe Group (Labor and Tierna Formation), in the vicinity of the hypabyssal body of Iza in the municipality of the same name in Boyacá, Colombia. Macroscopic observation, Plane Polarized Light Microscopy (PPLM), X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis, Raman spectroscopy and reflectance infrared spectroscopy in Short-wave (SWIR) to visible and near-infrared (VNIR) range were utilized. The results confirm the presence of these minerals and highlight the importance of a source of phosphorus and aluminium in their genesis as secondary minerals, interpreted as the product of infiltration of acidic meteoric waters through common phosphate rocks within the Guadalupe Group, combined with specific diagenetic conditions of pressure and temperature. Thus, a genetic model and the possible application of these minerals as geothermometers in sedimentary rocks are proposed. Furthermore, the relationship of these minerals with the hypabyssal body of Iza is highlighted, as well as their possible connection with archaeological sites of pre-Hispanic native peoples inhabiting the Cundinamarca highlands and Colombia. This first report in the Colombian Andes sets a precedent in establishing new sources of origin for variscite in Colombia, possibly used in pre-Hispanic trade routes and as a source of raw materials for the making of ancient jewellery.

Keywords : Phosphate; Hydrothermal; X Ray Diffraction; X Ray Fluorescence; Raman spectroscopy; Infrared spectroscopy.

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