Anorthosite is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar (90–100%), and a minimal mafic component (0–10%) including Pyroxene, ilmenite, magnetite, and olivine. These thin sections exhibit a rock which has been deformed and as such the once large plagioclase crystals have recrystallized to form much smaller crystals.

These thin sections exhibit beautiful crystals of olivine, pyroxene and augite, which often shows oscillatory zonation held within a matrix of plagioclase feldspar. The slides supplement the hand specimens nicely and are useful for interpreting the crystallisation history of the rock.

Obsidian, also known as ‘volcanic glass’ is a felsic, extrusive igneous rock. Crystal growth is minimal / absent within obsidian due to rapid solidification rates which inhibit crystal growth thus giving the rock a glassy appearance.

Pumice thin section slide exhibiting the highly vesicular nature of this extrusive igneous rock. Pumice lavas tend to be silicic or felsic which are highly viscous thus do not allow the gas bubbles to escape efficiently.This material was collected from the Lipari islands of Italy.

Syenite thin section slide. The thin sections show a dominant feldspar mass ( orthoclase ) with occurrences of hornblende, amphibole and clinopyroxene. Biotite mica may also be present however its occurrence is rare, The thin section is supplied in a protective card sleeve with a label, ideal for microscopy and educational purposes.

Volcanic scoria thin section slide exhibiting the highly vesicular nature of this extrusive volcanic rock. Typically volcanic scoria is basaltic or andesitic in composition; these magmas are typically runnier which results in a denser rock with larger vesicles.