Fluorite and quartz
Collection:
Cornish Mineral Heritage
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Fact sheet

Fluorite and quartz

Quartz (silicon dioxide) is a common mineral found in veins alongside the valuable ores.  Such commercially unimportant minerals are often termed gangue.

This specimen shows tall prismatic quartz crystals, along with an octahedral-shaped crystal of fluorite (calcium fluoride). It is part of the collection of minerals compiled by Cornish gentleman–collector Philip Rashleigh in the 18th century. It is illustrated in volume 1 of his publication Specimens of British Minerals and is described as:

"A double four sided pyramid of fluor, joined base to base, very large, semi-transparent, and of a light green colour, with six sided crystals of quartz. From Poldice, in Gwennap."

Poldice was active in the 16th century, making it one of the earliest recorded mines in Cornwall. Edward D. Clarke (later to become Professor of Mineralogy at Cambridge) descended Poldice on his tour of Cornwall in 1791:

"At about eighty fathoms we came to a vein of copper ore …. hardly room to move their bodies, in sulphurous air, wet to the skin and buried in solid rock …. pecking out the hard ore by the glimmering of a small candle."

Chemical Formulae: fluorite = CaF2 
quartz = SiO2

Specimen no. TRURI: 1903.1.938
Location: Poldice, Gwennap
Grid Reference: SW 740 427

Mindat Fluorite http://www.mindat.org/min-1576.html
Mindat Quartz http://www.mindat.org/min-3337.html

Additional images
 
  • Fluorite octahedron on quartz cluster, 6.5 cm across
  • Fluorite octahedron on quartz cluster, 6.5 cm across
  • Fluorite octahedron on quartz cluster, 7 cm across
  • Fluorite octahedron on quartz cluster, 10 cm across
  • Published illustration in "Specimens of British Minerals - Vol 1"
Map
 
50.240984, -5.17089
Precision:
Good
About this collection
 
Cornish Mineral Heritage

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

Collection: Cornish Mineral Heritage
Type
mineral
Category
secondary (gangue)
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:

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Cornish Mineral Heritage