Phonolite - Wolf Rock
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Fact sheet

Phonolite - Wolf Rock

This fine-grained porphyritic igneous rock comes from Wolf Rock, a tiny part of land that lies in the treacherous waters between the Isles of Scilly and Land's End. This island off the coast of Cornwall is best known for its granite lighthouse, built between 1861 and 1869, which covers most of the area above water. The phonolite was intruded around 130 million years ago and is one of a suite of alkaline intrusions of similar age.

The thin section illustrates the fine-grained igneous of groundmass of sanidine, nepheline and augite pyroxene. Phenocrysts are dominated by tablular sanidine, although there are rounded, embayed and sometimes altered nepheline phenocrysts also present (see rotation 1). Dark brown six sided euhedral nosean phenocrysts are also present and contain abundant inclusions. In places the nosean phenocrysts are partially altered to analcime.

49.9453, -5.8083
A small island between the Isles os Scilly and Lands End in Cornwall
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
Accessory minerals
Category guide  
Category Guide
Refers to any word or phrase that appears in the individual rock names. Names are generally descriptive; they allow users to search for broad terms like ‘granite’ as well as more specific names such as ‘breccia’. However, the adjacent descriptions of the specimens captures a wider range of general words and phrases and is a more powerful search tool.
Refers to any word or phrase that appears anywhere in the descriptions of the specimens
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.
Rock-forming minerals
Minerals that make up the bulk of all rock samples and are also the ones used in rock classi?cation.
Selecting one or more period, for example 'Jurassic'.
A term used to group together related samples that are not already gathered into a single Collection. For instance, there is a ‘SW England granites’ theme that includes such rock types as granite, hydrothermal breccia, skarn and vein samples.
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).
The owner of the sample that appears in the collection. For example, NASA owns all the samples that appear in the Moon Rocks collection
We would like to thank the following for the use of this sample: