Obsidian, Large Shelf Specimen 2kg

Description

Large Obsidian shelf specimen weighing 2kg from the Tarawera volcanic eruption of 1886 in the Bay of Plenty Region, New Zealand.

Formed during the eruption of Mt Tarawera near Rotorua in June 1886 at the margins of rhyolitic flows.  Contains pumice and perlite inclusions formed by contact with groundwater.

In the classroom, explore differences in structure compared to other rocks from felsic lava such as pumice or rhyolite.

Colour: black to black/green

Fracture: conchoidal

Mohs hardness :5-6

Specific gravity: ~2.4

Specimen pictured is actual specimen. Dimensions are 16x10x8cm and weighs just over 2000g.