Argillite

This specimen is a fine-grained, dark grey to charcoal-coloured sedimentary rock with a dense, compact texture and subtle planar fabric. It exhibits the characteristic appearance of argillite, a rock formed by the low-grade metamorphic hardening of mudstone or shale. Unlike shale, argillite does not split easily along bedding planes and instead breaks with more massive, blocky to slightly splintery fractures.

The elongated, blade-like form and smooth surfaces suggest either natural river or coastal transport, or deliberate trimming for use or reference. Argillite is widespread in New Zealand geological terranes, particularly within accretionary prism and forearc sequences, where fine marine sediments were compressed and lithified during tectonic convergence.

Due to the absence of an original label, this specimen is catalogued as argillite (provisional) pending further contextual, petrographic, or geochemical confirmation. It is retained as an educational example of fine-grained sedimentary lithification and early metamorphic processes.

183 x 43 x 30mm

269g