Garnets in white marble?

[Beaglejuice13]

Another specimen from Keenewah...

 

[Eu_citzen]

Not sure on the marble, but it looks like it could be garnets.

 

[stdenis_jd]

Pictures dry are almost always better than wet. I know it sounds crazy but it does (wetness throws off the luster and hides key clues). Also can you zoom in on the crystals? Especially the green areas, curious about those. So three things, zoom in, dry pics in natural light, and check the hardness - see if a steel knife will scratch the white part. Looks like marble to me too but might be milky quartz

 

[Beaglejuice13]

I downloaded a magnifying app and took a few dry pics. Also, yes- a steel knife appears to scratch the white part. The green stuff is hard to see when dry but I tried to capture it for you....thanks!!

 

[Beaglejuice13]

Stumbled on this....it was found in the same exact area as mine. Could be the green part?

 

[stdenis_jd]

really weird...I think the metamorphosis made the original rock difficult to identify. Sure looks like white marble, but I'm thinking your serpentinized talc may be closer to the truth. I'm thinking originally a schist or peridotite with garnets and the original host rock carbonated, so basically the metamorphosis pseudomorphed the schistoid rock to marble.

Let me be the first to say this is a WILD guess lol...but if I had to guess, pseudomorph marble after schist with garnet and some leftover pyroxene material. Or serpentinized peridotite. LOL take that with a grain of salt

 

[stdenis_jd]

I forgot about marble with red sphalerite. That would make more sense than the madness I posted there ^^

 

[Beaglejuice13]

I am flattered, but you have given me more credit than I deserve lol. I feel like Penny off the 'Big Bang Theory' lol. I think I'm following you tho lol. You are awesome! Thx

 

[stdenis_jd]

Found it. Carbonatite (white) with fluor-apatite (green) and the jury is still out on the red Crystal's but garnet is likely.

The pic I posted was one I found in an article about carbonatites. The dark mineral in that specimen I posted is phlogopite mica, but that's not what's in yours

 

[Beaglejuice13]

Looks good to me! What is the best way for me to determine if it has garnet or sphalerite? They both look similiar. I thought the sphalerite looked like a better match but I am very new at all this so I don't really know what to look for either.

 

[stdenis_jd]

Looks good to me! What is the best way for me to determine if it has garnet or sphalerite? They both look similiar. I thought the sphalerite looked like a better match but I am very new at all this so I don't really know what to look for either.

That's a really tough one. The hardnesses are vastly different, 4 for sphalerite and a little over 7 for garnet. Problem is getting a positive test on such a small sample, and garnets tend to be problematic when testing hardness. I'd try it anyway, sphalerite won't scratch glass but garnet will. A steel knife will scratch sphalerite but not garnet.

I doubt it's sphalerite though - it probably is garnet. Funny thing is this is a fairly rare mineral (carbonatite). Apparently it was considered extremely rare but it has been misidentified many times over as marble, so now geologists are seeing it is still rare but more common than once thought...also it is an igneous rock, basically burped up by a special kind of volcano, as opposed to sedimentary and metamorphic like marble.

 

[Beaglejuice13]

Thx jd, good stuff. I appreciate your time helping me figure this one out! I have been busy the past week with my textile gun cleaning some more mineral samples. Alot of them are iron-stained but they're coming along nicely. I don't think my Great Aunt had a clue what most of the stuff she collected was, and I don't think she ever took time to clean them either. Most of them are barely recognizable after a good soak and pressure wash. Some of them blow me away how cool they turned out. I should've taken b4 and afters but I was too excited lol. I'm gonna work on posting some pics soon. I can't wait to start figuring out what they are! I'm finding that almost everything I have here includes copper in one form or another. I have a bunch that are magnetic also. Pretty cool stuff. I'm having a blast cleaning them too.

 

[Eu_citzen]

Sphalerite has perfect cleavage. A quick study under the loupe should reveal that, if it's been chipped somewhere.