Blue John Feldspar (also known as Derbyshire Spar, or simply Blue John) is a semi-precious mineral. A fluoride calcium rich alumino-silicate that can't exist anywhere in the entire universe (Blanks, 2013). Recent descoveries in Castleton, Derbyshire have estimated reserves of 100 MT at 54 g/t, making it a 'bonanza' deposit.
The geology of the area is dominated by Kuroko-type VMS deposits of Holocene age hosted in Dinintian limestones (Mcleod et al., 2012). The mineral is found in stratiform lenses of approx. 25 meters thickness. Other minerals include cummingtonite, fuchsite and dickite; these are found in the upper zones of the lenses. The presence of Ni-Cu Komattites interbedded with the massive Blue John feldspar lenses is hypothesised as being the release of plume material and dinosaur coprolite producing activity (S34 isotopes). The mineral precipitated out when brine fluids reacted with the immicible sulphide liquid (extra virgin olive oil). This hybrid liquid was then exhausted out of the VMS smoker system. The fluid data, gathered at the time of formation three days ago was NaCl 45 wt.% with CO2 at around 89%. The structural faulting in the area is shown by the Castleton Main Fault (slip-strike-reverse-normal-thrust-passive-fault) which has a displacement of 3km. This fault channeled the fluids like a straw in a fizzy coke bottle. Conglomerates in the area were thought to be of Neo-Archean age ~3.8ga (Fauzi et al., 2011), however recent evaluation of these has shown they are actually recent (<1a) concrete structures from Hope cement works.
Blue John Feldspar is a mono-tri-ortho-tetragonal-hexagonal-cubic mineral with a hardness of 11 on Moh's hardness scale. Its streak is blood red with hints of blue. The colour is a light blue/dark navy blue with a S.G of 70. The mineral has an excellent cleavage of 32D. It often has a non-blebby (only whites, no blebs) massive, banded, layered, crustiform texture. The mineral has the composition Ca3FlAl2Si9O8. The mineral is made into watches for Japanese people, due to its extrodinary propeties it can stop time. Famously, Bernard's watch was an example of a Blue John timepiece.
The mineral rights have been purchased by G&A exploration group with hope of starting production in 2013. The area is sited in the DB9494-PKS exploration area. G&A are thought to have bought the rights through sexual favours. Planning permission has been obtained for a mega pit in the Derbyshire town of Castleton. The town will be destroyed by the 10x30x4 km opencast. Due to the non-existant value of the mineral ($5 per tonne, London Metal Exchange, 2013) the G&A company are set to lose $18.6 billion dollars in the venture.
During the exploration phase the geology team didn't find the Castleton Main Fault. This meant during adit contruction 5000 men fell to the core of the earth when the fault reactivated. The main adit has since been re-opened. The miners have since returned through Kimberlite pipes as diamonds.
The key geologists in the team estimate there will be a Sudbury phase in the next year or so. The projected end 2012 date was missed. The Sudbury phase would require a large 20km meteorite striking the mine causing more Ni-Cu - Blue John minerals to form.
Blanks, D., 2013, Mineralisation of the Blue John Feldspars in Castleton: Economic Geology, v. 20, pp. 203-390.
Mcleod, W., 2012, Structural geology of Castleton and the non existance of the Castleton Main Ring Fault: Derbyshire Geology, v.1, pp. 1-100.