Aragonite and associated minerals in hydrothermal veins found at Flintkote mine

First I would like to give due respect to Eric Tardiff who directed me to the area of dumped material with aragonite. With much back braking work He and later I moved material in the south end of the Flintkote cut. It is here, on the east wall, that the only noted occurance of rodingite appears in the Pennington sheet. That would be on the right side of the photo near the cliff in the distance. Also above this one can see what appears to be a slip fault. There are veins in the surrounding rock which produce aragonite associated with calcite, prehnite and other minor amounts of minerals.

The wall section showing the rodingite has been pretty much dug and picked clean. Without drilling and dynamite, it seems not worth the effort. The veins in the wall are too high and dangerous to get near. However some material has been accumulated in the dump material underneath. For anyone interested in aragonite crystals and the possibility of find some other minerals in micro-quantities this could be interesting. However, I most warn, that the money making green garnets are not found in these veins nor in this mine as far as I know.
The purpose of this article is to shed some light on the mineralization in these veins, which seem to contain aragonite, prehnite, vesuvianite and other minerals which are not fully identified. I will share my photos and identifications based on associations, environments and my level of certainty. Perhaps someone with more experience in this environment could help. Probably the best way is to send some samples to be tested by x diffraction or scanning electron microscopy.
I made three visits in the early autumn of 2007, digging the dump material searching for the aragonite. The following are examples:

The first plate is about 4”x3” with xls in the being about 4 mm. Second is about 1”x1” plate with bigger xls. The third piece is about 4”x3” with xls up to 10mm growing on another beige mineral.
Here is another look at the beige mineral magnified. I have not been able to identify this one yet. The field of view is about 4mm x 4mm. The mineral forms hexagonal prisms. In the same area I have found another mineral forming hexagonal plates Without further testing I can surmise the most likely minerals. Three minerals with possible hexagonal plate forms in this environment come to mind: magnesite, brucite and clinochlore. I believe the beige prisms are more likely to be magnesite, because it is known that in metamorphosism there is a chemical reaction where dolomite can break down to aragonite and magnesite. Or perhaps they are pseudohexagonal aragonite xls., formed by twinning.
The second mineral seems to be micaeous which makes me tend to think more of brucite or clinochlore. But they need testing. I am leaning toward brucite due to the environment and the waxy luster. Associated with this is the real mystery mineral. There is a creamy bluish botroiydal mineral I thought might be prehnite, because prehnite is found in veins near by. But looking at it makes one think of suolunite due to the bluish translucent look it has. The hardness of suolonite is 3 ½ and Prehnite is 6 by the Moh’s scale, so I will have to test the hardness. It is interesting how this botroiydal minerals forms blebs on top of the “brucite” xls. I will get to these later.
I would like to get back to the aragonite. I was mostly looking for aragonite. I ended up with a few flats of specimens, but the best was not until the last visit. I was digging into the talus like dumped material. I and Eric had some impressive pits carved out of the dump. I was digging about 3 ft deep and cutting under the buried rocks and roots until the side caved in, went through what fell in and continued. I started digging under a large rock (about 2 feet long) and I noticed some aragonite crystals showing and underside. Continued digging and it turned out to be the biggest piece. It is a 24” by 10” chunk with a whole face of aragonite xls. The crystals are straw colored prismatic forms.

I’d like to show you some of the close ups. Nice crystals around 12mm long. . And. Here we see lots of forms of prisms and domes terminating prisms forming tapering ends. Other ends appear more chiseled by some domes or sphenoids. Classic aragonite forms, orthorhombic bipyramidal. Oh, I almost forgot the clear xl showing prismatic faces and pyramidal terminations. The 10mm crystal in the 3”x4” pieces. Interesting flattened prisms (orthorhombic system has 3 different length, breadth and depths or three different axes. The ends seem cut by wedge, tent or domal shapes. Some of the prism faces may actually be prismatic faces (steep angle). In the background you can see the brown short pseudohexagonal prisms.
The crystals structures are interesting but the aragonite is fluorescent and phosphorescent as well. It gives a bluish cream medium bright fluorescence under the long wave and continues for a few seconds after the UV is shut off.
Here is a piece of prehnite I picked up in the same dumps. The thing must of originated in the same veins or close with the aragonite. It is a 2”x1.5” piece of blocky crystals joined in a crust. It has a light greenish color. Looking closer you see these isometric cubes. Pyrite? I’m not sure. It is black. Could be magnetite. Or chromite?
Well I have to say this one is another mineral needing identification.
lot’s of possibles.
Now the last photos are concerning the minerals associated with the mystery botroiydal mineral. I need help in identifying this one. Perhaps this is suolunite, but perhapse prehnite
This pieces is about 3”x3” and which was part of this group which I broke up from a larger piece containing small vugs. These are the rest. Six other pieces with the largest being about 6” long. Here is a magnified field of the botryoidal mineral. The field is about 10mm x 15mm. The color seems to be gray with a bluish tinge. The 5th photo above which seems to be brucite plates was found in this group of vuggy pieces as well. I also noticed another mineral forming small white needles on top of the “brucite” plates. It could be artinite. I am guessing due to the environment and association. Also I noticed this crystal which I am confident is vesuvianite, due to the crystal structure, associations and environment. In another part of the Flintkote dumps originating from the same part of the mine there were prehnite veins pierced with yellow idocrase blades.

---

In order to leave comments to this blog post, you must be registered