FMF - Friends of Minerals Forum, discussion and message board

[Tobi]

This amethyst is certainly from South America, Brazil or Uruguay.

[Jordi Fabre]

[Turbo]

[Turbo]

This is my beautiful Creedite that just arrived today. I was drawn to the color variation from fire orange, to salmon, and black. Crystals are very clear. The color is actually a little more pinkish than the photos show.

[Jim]

Thanks for posting your treasures! Keep 'em coming...

Cheers,

[Turbo]

I figured I post these because they're unique. They are part of a section of a curtain-like calcite stalagtite from Luray Caverns, Virginia, USA. These pieces were not removed for the purpose of selling, but were taken down for safety reasons.

[Turbo]

This Artigas amethyst is a new acquisition. Contrast this with the amethyst above, which I must add here, has goethite inclusions, suggestive of Brazilian origins?

[Turbo]

This is from the Anthony Gricius collection, now part of my own.

[Turbo]

Pseudohexagonal aragonite is one of my favorites.

[Turbo]

I love these two apophyllites from Jalgaon and Rahuri. The plate from Rahuri shows mostly intergrown pinacoid (pseudo-cubic) crystals with a few stilbite blades. The very haphazard arrangement of the pinacoid crystals struck me as different. The Jalgaon specimen was the most charming little thing when I first saw it! It's a single dually terminated green stripe apophyllite crystal perched on the side of a mound of apophyllite druse with a few stilbite blades here and there. There is not a single nick on this $14 specimen other than where it was detached at the base! The rusty color is slightly exaggerated in the photos. Enjoy.

13x6.5x4

[Turbo]

Another self-collected specimen from the Woodlawn Quarry, Wilmington, DE. This is a typical glinting pegmatite from this site composed of muscovite, white plagioclase, and quartz. Occasionally these pegmatites feature almandine as an accessory mineral. One of our members, Arthur Koch, tried to have us guess where his almandine on pegmatite was from. When I first saw it, I remember thinking how similar it was to mine. Arthur, if you're still around, I have the answer. Your specimen is from the quaint and little-know Woodlawn Quarry!

[Turbo]

Some new additions.

[Turbo]

It's been a while since I've posted. I have a few new additions to post, but I'll start with my favorite and put the others up a little later when I can get good photos.

Both danburites are from Charcas and have a slight pink tone when viewed against a white background. This is my first rough and cut pair! Very exciting!

[Turbo]

I love this one. Most of the shell itself is gone, but the negative space inside appears to be re-crystallized sand where it is not yellow calcite crystals.

[Turbo]

I apologize for straying a bit from traditional mineralogy with this specimen, but biology interests me as well. I am actually studying to be a dentist and enjoyed learning about the mineral content of teeth, so I though I'd share some of my knowledge for those who might be interested in the interface between biology and mineralogy.

Enamel is a calcium-deficient, carbonate-enriched hydroxylapatite containing traces of other Ca-P phases such as brushite, as well as 4% water. In individuals exposed to fluoride, a thin outermost layer of enamel features 10% replacement of OH with F, rendering this region more insoluble than deeper non-fluoridated regions. Its form is guided developmentally by cells called ameloblasts and proteins known as amelogenins that are removed in the final stages of tooth development.

In contrast, underlying dentin is 45% carbonated hydroxylapatite and 55% organic (collagen and non-collagenous protein). Tubules, occupied in life by the processes of cells that lay down dentin (odontoblasts) give dentin the chatoyancy seen here.