Amygdaloidal basalt - Rum
Collection:
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Microscope
Click the microscope button to view a thin section for this sample.
Microscope

Fact sheet

Amygdaloidal basalt - Rum

This rock comes from the Canna Lava Formation (post-Central Complex lavas located in NW Rum). It was intruded in the Paleogene during the formation of an ancient volcano, now deeply eroded, which in turn was part of the large North Atlantic volcanic province. One feature of the formation is that lavas are interbedded with conglomerates and plant-bearing sandstones, demonstrating the close association of the lavas with water and erosion of older rocks. The water may have contributed to the nature of this basalt flow, which has many holes (known as vesicles) formed by bubbles in the original flow. The holes are now filled by minerals that precipitated from the hot fluids that percolated through the lava after it solidified. This rock was collected from Bloodstone Hill on Rum.

The thin section specimen shows a fine-grained matrix that is mostly plagioclase, pyroxene and glass. Variations in staining appear to indicate water penetration varied within the rock, as did the alteration. Smaller elliptical vesicles appear to have been filled by a brown zeolite that shows concentric zoning, while larger vesicles contain radiating roses of chalcedony that grew from the walls inwards, eventually filling the entire space. The rock also contains plagioclase phenocrysts and one fragment of partially resorbed basalt with slightly larger plagioclase grains.

Map
56.99888, -6.3425
Description:
Isle of Rum, Scotland
Precision:
Good
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
basalt
Rock-forming mineral
plagioclase
feldspar
zeolite
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: