Quartz-tourmaline rock
Collection:
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Microscope
Click the microscope button to view a thin section for this sample.
Microscope

Fact sheet

Quartz-tourmaline rock

This sample is an excellent example of a prominent outcrop of quartz ‘shorl’ rock from Roche, close to the town of St Austell in SW England. The outcrop is part of the northern flank of the St Austell granite. Shorl is a local term for a tourmaline rich granitic rock, and this one represents a late phase of the St Austell granite body, that formed after most of the body had crystallised. It may represent the roof of the magma chamber. The outcrop consists of numerous interleaved pegmatite sheets and many cavities filled with quartz, tourmaline, zinnwaldite, and topaz.

The thin section consists of just two minerals; elongate and stubby tourmaline grains exhibiting blue/pale brown pleochroism and second order birefringence colours; and large plates of underformed quartz, exhibiting first order birefringence colours and high concentrations of solid and fluid inclusions that make them appear dusty.

Additional images
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

Type
igneous
Category
granite
Rock-forming mineral
tourmaline
quartz
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: