Obsidian: Rocks we know we knowDec 21, 2017
$5.50 inc GST
This green hornfels from a basalt source rock regionally metamorphosed by pressures induced by burial or crustal movements.
Blue hornfels located nearby was formed by metamorphosis of a shale and this greenstone (hornfelsed greenstone) source rock by a tonalite intrusion.
This green hornfels specimen is a typically foliated specimen rich in olivine. Commercially this rock is crushed and used in asphalt.
Images are examples of specimens only.
Size and shape may vary.
Specimens are usually no smaller than 75mm in one dimension.
67 in stock