FMF - Friends of Minerals Forum, discussion and message board

[PegmatiteAppreciator]

Hello Folks,

I've found a good amount of quartz crystals at my place, but some of these crystals have interesting habits/structure. I've read a little bit about elestial quartz, but some of these elestial-type looking crystals seem to bend at a right angle. its hard to adequately show without posting videos.

I have probably 20 more photos but uploading them on here is an absolute chore compared to most forums where you can upload them in seconds from your phone's gallery.

The main oddity is that octagon shape and some of the weird angled elestial/skeleton quartz habits. Is there a known cause for the octagon shape and the bent nature?

I've found examples for a lot of things on the usual websites, but nothing for that. I'd appreciate any insight you could offer. Thanks.

[Bob Morgan]

The octahedral face in your first photo is a prism face with three rhombohedral or termination face edges toward one end and three toward the other. The other two edges are of two adjoining prism faces.
In the fourth photo shiniest and the darkly coated faces are prism faces. The one to the top right is a rhombohedral face.
The last photo is of a mosaic structure with many slightly misaligned smaller crystals.

[PegmatiteAppreciator]

Thanks for the reply sir. I have a fair bit of that mosaic quartz that some folks call elestial or alligator quartz. Most of the crystal points i found are macro mosaic as well. Some of the quartz i find is trapezoid shaped.

Would you have any guess as to what causes these crystal habits? I've found about 20 crystals total on my land, lots of plutonic diabase, and I live near two faults that are believed to be reverse faults but that's about all of the info I can find on them.

I may have more than one kind of pegmatite on my place, but lately I've been finding a granite that reacts to UV with white, yellow, and a little bit of blueish/lime green.

I was hoping to look up some of the more odd crystal habits and use that as a clue for understanding my property. I've seen basic stuff on the internet but I suppose the best hope may be in older books. Would you agree?

Thanks again.

[Bob Morgan]

For quartz crystal morphology check out Mindat.org. It's in the quartz entry.
When it comes to identifying quartz faces, a face shape is determined by the faces adjoining it. I find it most helpful to identify prism faces first. They tend to have striations. Then I can orient the crystal with striations going from side to side of the faces. If the crystal has skewed development prism faces aren't necessarily side by side. That may be the case in photo 4.
Sometimes looking for a sixsided cross section will reveal the prism faces on the six sides.
Other faces are toward the crystal terminations - nearly always rhombohedral faces, although there can be others that are rarely prominent.
Again, a crystal that had skewed development might have an odd shaped face. Most of those will be one of the terminal faces that has an adjoining prism face with edges of other terminal faces - mostly rhombohedral - at the other edges.
All my odd shaped quartz crystals fit that description.
I see you are in Virginia. The Richmond club has very active collectors who probably could help you. Having someone hold and rotate the crystal makes it easier to find the identity of a face.