New discovery of pargasite and forsterite phenocrysts in basalts, suggesting significant geological implications.
The new occurrence of pargasite and forsterite phenocrysts was discovered in basalts in the area of a former field near the Očová village, Zvolen Co., Banská Bytrica Region (central Slovakia). Pargasite forms vitreous dark brown to black crystals up to 6 cm in size. Its chemical composition shows dominant Mg2+ (3.07 - 3.16 apfu) followed by Fe2+ (0.84 - 1.00 apfu) and elevated Ti (0.22 - 0.27 apfu) at the amphibole crystallochemical C site with the average chemical composition (n = 15) A(Na0.58K0.35)B(Ca1.83Na0.11Fe2+0.05Mn0.01)C(Mg3.12Fe2+0.92Al0.62Ti0.25 Fe3+0.10V0.01)T(Si5.97Al2.03)V O22W[(OH)1.99F0.01]2. Forsterite crystals have vitreous lustre with greenish to dark yellow colour, reaching up to 16 mm in size. Its chemical composition corresponds to the average endmember formula (n = 15) as Fo88.9Fa12.6Tep0.2. This find represents an occurrence of unusually large crystals of pargasite associated with forsterite in igneous rocks of the Neogene Poľana stratovolcano.
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Myšľan et al. (2025) studied this question.