Biotite granite - Luxulyan
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Fact sheet

Biotite granite - Luxulyan

This sample of biotite-rich granite comes from the Luxulyan quarry in the Luxulyan Valley in south east Cornwall. This sample is a less evolved portion of the intrusion, which was associated with the tourmaline and topaz-rich intrusions and mineralisation. The valley is part of a World Heritage Site containing the remains of extensive early 19th century industrial activity, including mining and quarrying, which at its peak included several water wheels and steam engines.

The thin section illustrates the quartz-rich nature of the rock, which also contains altered orthoclase, plagioclase and both biotite and muscovite. The biotite is notably rich in pleochroic haloes, indicating a high proportion of zircon and monazite crystals.

Additional images
  • granite - width 2.8 cm
  • granite - width 2.8 cm
  • granite - width 9.5 cm
50.3986, -4.7409
Luxulyan quarry, Luxulyan, near St Austell, 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: