Cassiterite-Tourmaline Vein - Restowrack (#44)
 >View Microscope
 >View Object
Fact sheet
Description: 

The often euhedral shape of the tourmaline crystals in this sample suggests early crystallisation in a relatively open vein. The deep blue colouration of the tourmaline is typical of hydrothermal tourmaline in the St Austell granite complex (and distinct from magmatic tourmaline which is usually brown). At some point during the development of the vein, tin became concentrated in the passing fluids and crystallisation of cassiterite followed. Spaces in the vein were mostly filled at this point apart from a few small voids that were later filled by needles of blue tourmaline and finally quartz.

Veins such as this were of major importance to the tin miner and Bunny mine was established elsewhere in the complex to extract not only cassiterite, but also wolframite (the main ore species of tungsten). The beam engine from Bunny mine (1850) has been restored and is now part of Poldark mine, a local tourist attraction at Wendron, near Helston.

Tin mineralisation in the St Austell granite complex has been measured at 271 ± 4.5 Ma.

In Place
In Time
Location description: 
Restowrack china clay pit, near St Dennis, Cornwall
Accuracy:
Location precision: 
Moderate
Timescale:
Timescale: 
Permian
Ma = Millions of years ago
In Focus
Collection:
What\
Type:
Type: 
igneous
What\
Rock-forming minerals:

Rock forming mineral:

What\