East Wheal Towan exotic semiconductor field trip
More actions
One of the tasks I've been funded to do is "Researching mine history and searching mine sites for semiconducting material", and for the first trip of this project I decided to head to the north coast to check out a few places:
These are all within a short walk of each other near the cliffs between Porthtowan and Chapel Porth beach.
And on the way back:
The reason for these choices are that there are many semiconducting minerals that are very commonly found on the mine waste dumps in Cornwall, but I've been wanting to expand the possibilities a little. There are two that I've tested in the past but haven't been able to find enough of to use much.
- cuprite a red transparent copper oxide - common is some copper mines but not others, I think this is to do with the temperature of the mineral formations. I've found well formed but tiny specimens before, but the Porthtowan area seems to have larger amounts of less well crystallised material - perfect for use as natural semiconductors.
- wolframite an ore of tungsten, which Nangiles mine was used for mining at one time. I've seen negative resistance in this mineral before, which has potential to build more interesting circuits.
East Wheal Towan turned out to be quite abundant, I think because it's a minor site that not many people have been to (added to the fact it's surrounded in very prickly gorse I had to carry the dog over). Most of the minerals I found had very coarse crystallisation with nicely formed faces.
This is a specimen I found with arsenopyrite, galena and sphalerite all hosted inside a matrix of well formed quartz and green chlorite. None of these are rare, but it's satisfying to find all of them in one small sample - and given that previously there were no confirmed minerals listed on the mindat.org locality it means I could add them all in one go.
The sharply defined silver crystals are arsenopyrite, the darker clusters on the top left and lower middle are galena and the grey mass on the right above the vein of arsenopyrite is sphalerite.