FMF - Friends of Minerals Forum, discussion and message board

[cascaillou]

Hi,
I found an outcrop of granitic pegmatite in the Pyrénées mountains, with some embedded Schorl (tiny broken prisms and anhedral ones). Indeed, in this area, pegmatites do not host pockets filled with crystals, instead the crystals are found directly embedded within the rock.
So, I wish I could find better Schorl crystals (meaning large and well crystallized) within this outcrop, but I'm not sure where to start digging:

Some parts of this pegmatite outcrop are rather fine grained (5mm to 1cm grains), while other parts are more coarse grained (1 to 4cm grains). Many parts of the pegmatite outcrop are mostly feldspatic (association of bluish grey and cream white feldspar grains) while other parts have more quartz, usually without major mica although a few areas do show large mica plates.

So, in your experience of European pegmatites, which parts of the outcrop sound more appropriate for nice Schorl crystals to occur?

[Peter]

[cascaillou]

I was wondering if Schorl is more likely to occur in the feldspatic part of the pegmatite outcrop, or rather in the part that has more quartz.
It would be difficult to take a picture due to thick vegetation and moss.

[Peter]

You may have in both.
The largest schorl I have seen occured in primarily feldspar blocky zone boardering the quartz core in very large pegmatites.
However the easiest schorls to recover complete with hammer and chisel, or perhaps you have access to more sophisticated tools, are in quartz.
Peter

[Peter Lemkin]

In the pegmatites I'm familiar with, the schorl will be more solid [less likely to easily crumble - but don't confuse this with weathering] as you get near the area of possible pockets. When you are very close to a pocket the tourmaline will actually have the XX oriented toward the core. So, I'd look for areas that have schorl that are more tough than others [don't break apart, but stay consolidated more often from the quartz]. There are other 'tricks' one learns in pegmatite areas...but you don't yet know if there are pockets or not. Pockets sometimes are penetrated by roots of trees/bushes.....but that is easier to find in semi-desert areas where there are not many plants. I'd also look for mica, especially lepidolite, lying on the ground in areas that might have pockets...but that is not 100% either. In each pegmatite area people learn the 'signs'...although there are a few that hold for most pegmatite areas. Not all pegmatites have pockets...in fact, most do not. Graphic granite is another thing I look for, as well as albite xx. Bigger and better garnet xx might be another indication. In some pegmatites, phosphate minerals, such as purpurite, are indications....I think you should do some research on the area you are exploring to see what has been found and what good signs are. If there are any ravines that water has moved materials down...walk back up and watch for xx that seem promising and find out where they might have come from. Look for others prospect holes, if any. See if any mining claims in the area and what kinds of minerals were on the claims. After years of searching pegmatites one gets a 'second sense' for where pockets are....and it is hard to explain to others [or one doesn't want to in very good areas ;-) ]

[Josele]

[cascaillou]

Thanks guys, great contributions!

[Philippe Durand]

I have a little experience of french pegmatites south of massif central.
I have found some schorls ;
but I have worked the ground around and down at the foot of the pegmatites or on altered pegmatites; it is far easier to work, and to find crystals naturally free from the quartz and
feldspath.

examples that can be found

[cascaillou]

Well I spent the all day there but couldn't find anything interesting.
Still here are a few pictures. The first pic shows the host rock surrounding the pegmatite lodes. The other pics show the pegmatites.