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[R.U. Sirius]

I've found this pair of small slabs in a large (and mostly unlabeled) collection I purchased.

Parts of it look very much like fluorite - translucent purple with fibrous structure. But then some of it is orbicular and still gentle purple or lilac in colour. Note the structure is not stalactite - you can see from the side that these are indeed orbicles.

I dusted off my hardness kit, but the results were inconclusive, so I'd rather not say anything.

10% acetic acid (which in my experience produces effervescence with all calcites and some dolomites) did not produce any bubbling, apart from one small area of outer crust - no surprise there.

Splintery fracture is apparent in the lower right corner of the reflected light photograph.

There is very faint, white fluorescence with 365nm excitation from the orbicular centres, but really nothing impressive.

I am hoping to learn what this might be before I take it to the saw...

Thank you for any insights!

[irockhound]

With the fibrous radiating structure I might go with Mexican Smithsonite.  Since I don't want to post any possible copyrighted image here is a website that deals in Smithsonite from the refugio mine and it is pink/purple and green in combo.

http://www.treasuremountainmining.com/index.php?route=pavblog/blog&id=64

I think this is your material

[freeformcabs]

I would say that is Luna Moon agate from Mexico.

[irockhound]

I could be wrong for sure but I often see some pretty wild guesses here on the forum but here is more of the reasoning why I came to the choice I did and why I do not think it is agate.  As it is hard to identify things from a picture I try to use all clues in the picture and not just the color or pattern.  The fracture on the fan on the bottom right is not the type you associate with agate as it has defined patterns of crystal growth.  Also in that same fan where it transitions thru the milky color band, in agates this is "normally" a solid and here you can see the fiber extend thru that band.  2nd is the formation of the material as you can see in the center of the image where you can see acicular crystal growth as you do in Malachite, Smithsonite etc..

I'll look for a slabbed piece of Smithsonite to show as comparison but that will get added later today.

Sorry about the writing on the picture but I have a hard time writing with the mouse.

This is a close up showing the structure of growth in smithsonite and how the structure goes thru the bands like in your material.  Agate does not grow like this.  see 2nd image

[Ryaly2dogs]

Fascinating to follow this thread.  I learn much by following this forum.

[irockhound]

One other thought.  You also mentioned that you used 10% acetic acid and from what I found Vinegar is no less that 4% acetic acid and is normally higher.  Acetic acid is a very weak acid unless at higher percentages.  Since Smithsonite is not the same as pure calcite it does not dissolve as easily using acids but it will depending on the strength and type of acid.  People using Muriatic (weaker Hydrochloric) have used it to gain a more polished surface to Smithsonite since it is slow enough that does not destroy it like it would a calcite so you would still not expect a very active boil or fizzing like from a calcite without the impurities of smithsonite.

[R.U. Sirius]

Thank you for the insights! I am definitely leaning towards a carbonate of some kind, and smithsonite might be the one. One of the confusing bits is the hardness - while I wasn't able to produce conclusive results, it seems to be quite hard (6 or 7 at least). Is it possible that smithsonite get silicified to some degree, leading to increased apparent hardness? I remember someone explaining how this happens with magnesite sometimes.

[irockhound]

Did you get different hardness results on different parts of the material?  Smithsonite quite often has numerous other Minerals forming around it.  As for hardness for smithsonite I think you are stuck at 4.5 unless someone with more Scientific experience could add their voice to this.  Can Smithsonite be mixed with another silicate, I am not sure.  I am sure you could have multiple minerals in the same slab though which was the reason for the mixed hardness result question.

[freeformcabs]

Ive actually heard some people say Luna Moon Agate was a silicified Smithsonite.

[R.U. Sirius]

Ive actually heard some people say Luna Moon Agate was a silicified Smithsonite.

This would explain a lot. For what it's worth, I've found a number of very similar rocks online labeled as Luna Moon Agate, so that's what I'll call this for now!

[gemfeller]

It looks just like Luna agate I've cut.  It makes great cabs.

Luna (500x353).jpg (105.2 kB . 500x353 - viewed 217 times)

[R.U. Sirius]

Also, it just dawned on me that we should stop calling it "Luna Moon"... it's the same word in two languages.

[irockhound]

So whats wrong with moon moon, they name pandas like that lol

[R.U. Sirius]

So whats wrong ?with moon moon, they name pandas like that lol

And proper scientific name for the western gorilla is... Gorilla gorilla.

But we digress. I should really try and cut this beautiful stone!