Kaersutite theralite - Lugar sill
Click the microscope button to view a thin section for this sample.
Click the microscope button to view a thin section for this sample.

Fact sheet

Kaersutite theralite - Lugar sill

This sample derives from the 49m thick Lugar sill in Ayreshire, Scotland, an alkaline sill intruded around 288 million years ago during the Carboniferous period. The sill was intruded as at least four separate phases (indicated by marginal chilling between the bands) ranging in composition from theralite passing down into kaersutite theralite and then picrite. It is thought that the magmas were produced in a deeper magma chamber by differentiation of a mantle-derived, alkali-rich picritic magma. The site is a protected Site of special Scientific Interest (SSSI).

The thin section contains large blades of brown pleochroic kaersutite amphibole, end sections of which exibit 120 degree amphibole cleavage. There are also many tabular plagioclase grains showing some alteration. Pale coloured nepheline and analcime are also present and exhibit low birefringence colours. Altered pyroxene was probably originally titan augite.

55.4666, -4.2166
Lugar Sill, Ayreshire, Scotland
About this collection

The United Kingdom Virtual Microscope (UKVM) collection consists of igneous, sedimentary and metamorphic rocks from around the UK.

It is intended as a teaching resource, helping to tell the story of the common rock types and how they form, and reflecting the history of the UK at the margins of the continent of Europe. The collection is a series of teaching sets, for example igneous rocks from the North Atlantic Igneous Province and SW England; high-temperature metamorphic rocks from Scotland and low-temperature metamorphic rocks from Wales; and sedimentary rocks, including English limestones and sandstones.

Sample details

Rock-forming mineral
Category guide  
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Accessory minerals
Minerals that occur in very low abundance in a rock. They are usually not visible with the naked eye and contribute perhapssver, they often dominate the rare elements such as platinum group metals.
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A general term used to label a rock sample. It is a useful way of grouping similar samples throughout a collection. Category names are often, but not exclusively, common rock names (e.g. granite, basalt, dolerite, gabbro, greisen, skarn, gneiss, amphibolite, limestone, sandstone).
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We would like to thank the following for the use of this sample: