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Fact sheet


Cassiterite is the major ore of tin, which is the most important metal sourced in Cornwall. It is found in veins associated with granite. The elongate, pointed prismatic crystals of this specimen are called sparable crystals from their resemblance to sparrows’ bills and also recall the headless nails used in the soles of miners’ boots. This specimen came from Dolcoath in 1858. 

Dolcoath’s early life was as a copper mine, but by 1832 it was becoming unprofitable. However, the mine captain, Charles Thomas, was convinced that rich tin ore could be found in a zone below that being worked for copper. He persuaded a new group of shareholders to invest in the tin potential of Dolcoath. The venture paid off and rich tin was encountered at depth. Dolcoath returned its first profit as a tin mine in 1853 and became the deepest mine in Britain. It operated until 1921.

Chemical Formula: SnO2

Specimen no. TRURI: 1922.13.119
Location: Dolcoath mine
Grid Reference: SW 662 405


Additional images
  • Cassiterite 4 cm across
  • Cassiterite 4 cm across
  • Cassiterite 9 cm across
  • Cassiterite 3 cm across
50.216602, -5.33471
About this collection

This Collection focuses on Cornwall and West Devon’s mineralogical and mining heritage.  The specimens it features are drawn from the collection of the Royal Institution of Cornwall (RIC) held at the Royal Cornwall Museum (RCM). 

This collaborative project involving the RCM, the Cornish Mining World Heritage Site and The Open University explores how access to the RIC’s mineral collection and the stories it can tell can be widened using digital technology.  It includes radioactive minerals from Cornwall that would otherwise be inaccessible to the public for health and safety reasons.

Sample details

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: