Harkerite crystals; Appian Way roadcut, Albano, Lazio, Italy; KS; unique piece

Harkerite crystals from Albano, Lazio, Italy

This specimen displays an irregularly shaped, predominantly whitish-gray matrix with beige to brownish areas and scattered dark inclusions. Numerous small, lightly shimmering crystals and lustrous patches are visible across the rough, granular surface, forming closely intergrown structures in places. The varying shades and diverse surface textures give the specimen a distinctive appearance. Particularly noticeable are the contrasts between the light-colored mineral areas and the dark gray to black sections.

Geology & Locality

Harkerite is a rare calcium- and magnesium-rich borosilicate containing additional carbonate groups. The mineral was named in 1948 after British petrologist Alfred Harker and is particularly associated with contact-metamorphic rocks. Its type locality is on the Isle of Skye in Scotland, where it occurs in skarn formations. This specimen originates from a roadcut along the historic Appian Way near Albano in the Italian region of Lazio. The surrounding area forms part of the volcanic Alban Hills southeast of Rome.