Luxullianite - Luxulyan (Tregarden) quarry (#02)
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Fact sheet

Luxullianite - Luxulyan (Tregarden) quarry (#02)

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
  • width 13.5 cm
  • width 5.7 cm
  • width 13.5 cm
  • width 13.5 cm
50.399553, -4.742661
Luxulyan (Tregarden) quarry, Luxulyan, St Austell, Cornwall
About this collection

A case study of the St Austell granite complex in Cornwall, England, illustrating the range of rocks associated with a granite intrusion. The earliest part of the complex is a siderophyllite (biotite) granite containing muscovite and tourmaline typical of a SW England granite, with many primary magmatic features.

This early intrusion was followed by the intrusion of an evolved volatile-rich magma which was the driving force behind a series of intense hydrothermal processes as volatiles escaped from this magma and helped to establish an extensive alteration halo (aureole). Boron, fluorine and lithium (as well as water) played major roles in the formation of the second intrusion and in the associated hydrothermal processes. Igneous activity lasted around 18 million years from 282 Ma (siderophyllite granite) to 265 Ma (fluorite granite).


Sample details

Collection: St Austell Granite
Rock-forming mineral
Category guide  
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.
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).
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We would like to thank the following for the use of this sample: