Blaen y Nant Molybdenum 'Mine'

[RobinGriffiths]

Sunday 13 August 2023

William Williams, in his Observations of the Snowdon Mountains noted in 1802 that A little below Blaen y Nant farm-house there is, at the foot of a high rock, a large body of some mineral matter, not unlike to what miners describe by the name Molubdena…

This was a quick visit, needing only a few hundred metres of walking from the minor road in the Ogwen Valley opposite the A5. An adit of sorts is immediately visible at the base of a small outcrop. There's a rib of rather rotten looking reddish brown rock that may be the 'vein'. It is covered by a yellow crust which I'm taking to be gypsum maybe stained by limonite.

A alippery grassy path leads to the top level which turned out to be 6" deep with water an led to a small muddy chamber. Again some browny red stuff, but nothing wildly impressilve.

Lower down is a buried spoil heap, and below this what may be the infilled remains of another adit. Most of the material on the heaps looked to be iron impreganted shales, with some rotten pyrites in places. Very irony would be the verdict. One sample looks to have a lustrous grey sheen, but I've yet to examine this properly to see if it's molybdenite.

Bottom Adit at base of small outcrop, Top Adit below top outcrop.

Bottom Adit - Yellow crusty stuff

Top Adit Entrance

Top Adit

 

[Graigwen]

Molybdenite tends to have thin flakes. These easily bend without breaking - this gives quick diagnosis.
I think I was in that mine one Sunday afternoon 52 years ago, I don't remember molybdenite there but it is certainly the right area. There are tiny flakes (really tiny!) in the rocks of the retaining wall alongside the A5 on the opposite side of the valley. There is also a lot of pyrrhotite in those rocks and when doing a survey I found a large compass deflection. (The deflection was so large at one spot that I think something other than just pyrrhotite was involved.)
.

 

[jonj]

Molybdenite tends to have thin flakes. These easily bend without breaking - this gives quick diagnosis.
I think I was in that mine one Sunday afternoon 52 years ago, I don't remember molybdenite there but it is certainly the right area. There are tiny flakes (really tiny!) in the rocks of the retaining wall alongside the A5 on the opposite side of the valley. There is also a lot of pyrrhotite in those rocks and when doing a survey I found a large compass deflection. (The deflection was so large at one spot that I think something other than just pyrrhotite was involved.)
.

Molybdenite is very soft and smears when scratched with a finger nail

 

[Mrs Trellis]

Remember that the Greek for lead is μόλυβδος. This may be romanised as molubdos by academics who had Ancient Greek ( a modern Greek phonetic romanisation would be molyvdh*os (*dh like the th in "this" but not as in "thin" (θ))). It was first isolated in the late 18th. C about 20 years before the article.
I rather think that the miners probably got the term from an academic geologist who had Ancient Greek as normal for University educated people at that time (1802) who possibly didn't know the welsh word for lead.

 

[RobinGriffiths]

There's little doubt that molybdenum was found in the mine https://museum.wales/mineralogy-of-wales/database/?mineral=315&name=Molybdenite

However, it does seem odd that they'd be mining a mineral in 1802 for which there would be no industrial use for almost a century. So I guess they were just following some orey ground to see what they could find rather than mining the molybdenum.