UK: Nepheline Syenite
Click the microscope button to view a thin section for this sample.
Click the microscope button to view a thin section for this sample.

Fact sheet

UK: Nepheline Syenite

This nepheline syenite is part of a dolerite intrusion at Cnoc Rhaonastil, Isle of Islay, Scotland that formed in the Paleogene period as part of the North Atlantic volcanic province. The rock is unusual in that the magma evolved from alkali olivine-dolerite by crystal fractionation at low pressure. The intrusion is an example of an upper-crustal magma chamber, in which the alkali olivine-basalt magma crystallised in situ. Research has shown that this represents the distended head of a large dyke in which a single pulse of magma was emplaced and subsequently crystallised without significant interaction with the local country rock.

The thin section contains green-coloured aegirine pyroxene with characteristic patchy colour variations, biotite mica, and large grains of nepheline that have undergone alteration and exsolution to plagioclase. Isotropic analcime completes the main assemblage. Patches of zeolite are also present, exhibiting characteristic radial growth patterns (rotation 1).

Additional images
  • width 7 cm
  • width 2.7 cm
55.752668, -6.089344
Cnoc Rhaonastil, Isle of Islay, Scotland
About this collection

The Ilimaussaq alkaline complex is the type locality for agpaitic nepheline syenites and represents an enormous concentration of rare elements, notably Li, Be, Nb, Zr, REE, Y, Th and U. Around 220 mineral species have been identified. We can't identify all the minerals present in these samples. Email us at if you can help.

Note we have recently expanded the collection to include other syenite complexes worldwide.

See also Alex Strekeisen's great website for more information on syenite complexes.

Sample details

Collection: Greenland
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: