Piemontite metaquartzite
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

Piemontite metaquartzite

This sample was found to the NE of Ben Hope in the far north west of Scotland. It comes from the "famous" diamond locality described by John Faithfull in the Scottish Journal of Geology (2007, volume 43, pages 33-40). It is a pink mica-rich quartzite, with small quantities of tiny dark-red, black and colourless crystals. It was the colourless garnets that led Matthew Forster Heddle (in the late 1890's) to suggest diamonds may be present in the rock. The recent investigation has confirmed that the "diamonds" are instead garnets. The sample is from an erratic boulder, but is almost certainly derived from local Moine rocks.

The sample contains an oxidized manganese-rich silicate and oxide assemblage: piemontite, muscovite, spessartine (Mn-rich garnet), K-feldspar, hematite, braunite, and rare zircon. Rotations 1 and 3 focus on the piemontite which is remarkably pleochroic, whereas rotation 2 shows the Mn-rich muscovite, more piemontite, iron/manganese oxides and tiny colourless garnets. Look closely as the garnets are difficult to see.

Additional images
58.430482, -4.617004
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

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: