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. Syenite or larvikite is defined as a monzonitic plutonic rock and is almost entirely composed of feldspar. Due to its geochemical characteristics and its chemical composition (it contains Ca, NA and K) the so-called 'ternary' feldspar it is believed to have formed at around 30 km, close the the boundary between the crust and the mantle. The rock was collected by staff from the type location, Larvik, Southern Norway. Each section is made to 30 microns thickness and the glass is 46 x 27 mm in size with a cover slip. Supplied in a protective card sleeve with a label, ideal for microscopy and educational purposes.