Luxullianite - Tregarden
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Fact sheet

Luxullianite - Tregarden

Luxullianite is a rare type of tourmaline-rich granite named after the village of Luxulyan in Cornwall. Luxullianite is formed from boron-rich pegmatitic fluids caused by fractional crystallisation of the biotite-rich St Austell granite complex, which formed around 280 million years ago by partial melting of the lower continental crust during the Variscan orogeny.

In hand specimen the rock appears to consist of two main parts – striking salmon pink tabular feldspar shapes, and black tourmaline that appears to be infilling. Luxulyan quarry is a large (now water-filled) hole on the outskirts of the village. The quarry has been designated an SSSI (site of special scientific interest), and access and collecting is not normally possible.

In thin section the large feldspar shapes that appear pink in hand specimen are only partly transparent and appear dark. The feldspar grains exhibit some features characteristic of feldspar, and their partial alteration to kaolinite and sericite is part of a sequence from pure granite to clays in our collection of SW England granites. The other minerals present are tourmaline, white mica and quartz. Radial tourmaline crystals growing into cavities are visible in this thin section but are much better developed in other Luxullianite samples in the collection. 

Additional images
  • luxullianite - width 14.5 cm
  • luxullianite wet - width 13.5 cm
  • luxullianite - width 13.5 cm
  • luxullianite - width 5.7 cm
  • luxullianite - width 14.5 cm
50.398552, -4.740911
Tregarden quarry, Luxulyan, St Austell, Cornwal
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  
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: