Luxullianite - Shabby Rocks Field
Collection:
UK Virtual Microscope
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Fact sheet

Luxullianite - Shabby Rocks Field

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 earlier 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 voids. 

This sample of Luxullianite illustrates two phases of tourmaline crystallisation: an early blocky magmatic phase exhibiting characteristic tourmaline colours, and tourmaline radial sets of needles forming ‘suns’ that grew late in the formation of this rock. Crystallisation in cavities has allowed the rock to develop fine rosettes of acicular crystals with characteristic brown-blue-green pleochroism and vivid birefringence. Zircon and the tin ore mineral cassiterite complete the mineral assemblage.

Additional images
 
  • luxullianite - width 5.6 cm
  • luxullianite - width 10.2 cm
  • luxullianite wet - width 9.7 cm
  • luxullianite - width 9.7 cm
  • luxullianite - width 9.7 cm
Map
 
50.378591, -4.748199
Description:
Shabby Field, near Luxulyan, St Austell, Cornwall
Precision:
Good
About this collection
 
UK Virtual Microscope

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

Collection: UK Virtual Microscope
Type
igneous
Category
greisen
Rock-forming mineral
tourmaline
quartz
orthoclase
feldspar
Category guide  
Category Guide
Title
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.
Description
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.
Timescale
Selecting one or more period, for example 'Jurassic'.
Theme
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.
Category
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).
Owner
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:

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UK Virtual Microscope