Four unknown rocks

I have four unknown rocks that I acquired recently, unfortunately without any clues to origin or what price was paid for them.

The first has a light green, silvery ('metallic') color. The second has some red and black parts on a white (quartz?) matrix. The red color looks like some Erythrin pictures I've seen. The third has a shiny peach like color, again somewhat 'metallic' looking. All three of these are very soft, in the sense that I can scrape/tear off pieces by just using a fingernail. The fourth is very heavy in comparison and has baryt (?) on the back. The fourth is only somewhat larger than the second but weighs a good 100 grams more (160 grams vs 263 grams).

I will post the other three pictures in the next post.

If someone has an idea of what these rocks are, I'd appreciate it.

The remaining pictures.

These are guesses based on the photos:

1) mica - fuchsite
2) the red appears to be platy like mica, so it could be a type of mica, other thoughts based on the appearance of the other matrix minerals are possibly tourmaline or eudialyte but eudialyte is not platy so I would rule that one out, unlikely tourmaline (rubellite) so I would stick with mica.
edit- based on your observation that they are soft would suggest mica as well
3) mica and iron stained quartz?
4) same as 3
5) possibly franklinite, but the dark crystals are not complete so difficult to tell, otherwise it could be one of several black minerals.
6) baryte/barite

I counted 5 specimens unless 5 is the underside of 6 in which case then it is not franklinite as it is not found with baryte.

regards,
stephanie



Edited 1 time(s). Last edit at 06/15/2012 01:11PM by Stephanie Martin.

Many thanks for your reply Stephanie. The fifth picture is indeed the underside of the sixth (4a and 4b is one specimen), making 4 specimens in total (the fourth picture is the underside of the third, so 3a and 3b is one specimen also).

Daniel

Hi Daniel,

The heavy one should be the baryte, the last photo. If #3 is heavy then it could also contain baryte rather than quartz, there is no crystal shape to discern in the photo. If it is soft as you indicate this would also lean more towards baryte.

For the back of the baryte, I would suggest the black crystals are some type of amphibole based on the diamond shaped cross sections that I see.
But that's just a guess.

regards,
stephanie



Edited 1 time(s). Last edit at 06/15/2012 02:46PM by Stephanie Martin.

#1 looks like it has a greasy lustre, that's why I think it could be talc...
cheers

Hi Daniel;

#1 Looks like Sericite (mica alteration product from... Corundum, or other minerals) Usually silvery, but may be tinged.
#2 White mineral is likely Albite. Red mineral may be Lepidolite Mica, though this is quite dark. Hard to say.
#3 Agree with Stephanie, likely mica and quartz. Might be from the same place as #1.
#4 Baryte for sure. The blades and the way the blades are oriented is somewhat a telling feature with this mineral.

Unfortunately, it is hard to tell where any of the specimens may have come from as the mineralogy assemblage and crystal form is not distinctive to one locality.

Hope this helps.

Andrew Haighton,
Brampton, Ontario

Thanks all for the help! The Baryte is clear then, and by comparing with other pictures online I like the Fuchsite suggestion for #1 from Stephanie as well. I'll note the others as Mica for now, along with the other possibilities for them.

Regards,
Daniel

Hi Daniel,

You could test for carbonates with small sample scrapings into HCL or vinegar for the white minerals, that would rule out things like calcite.

The red mineral is most likely muscovite mica, as it is the wrong assemblage for erythrite as you had thought, and the other minerals I mentioned are either too hard or the form is not correct. Here is a picture of a red muscovite from the gallery:

[www.mindat.org]

regards,
stephanie

Very nice regardless of what they turn out to be! ide rarther find a ton of a puzzel to be solved than a ton of gold, !!! I know i would be happy with searching for the answer, but not so sure having the gold would make me as happy !

Hello Daniel,

I think the first one is one of the chlorites, a typical dark green mica-like mineral. If it is, it should cleave off in flakes. They should be flexible, but snap back when released. If it is really soft, scratched easily with your fingernail, and feels greasy, it would be talc, but I kind of doubt it.
The third one looks like spathic iron ore - siderite. If so, it cleaves in rhombohedrons, is yellowish (maybe inside) to dark brown on the outside, when powdered will dissolve with bubbling in hydrochloric acid (I don't think it will bubble in vinegar, not sure).
The sixth one is interesting. If it is extraordinarily heavy, it would most probably be barite. If it is not heavy and you can easily scratch the face of a plate with the end of a copper wire, it is probably gypsum. There are other possiblities, but I would stay with one of those for the moment. Can you get a streak by making a mark on the bottom rim of a coffee mug with it.

Given the lighting, the first sample reminds me of serpentine.