FMF - Friends of Minerals Forum, discussion and message board

[Rei]

If the analysis says that the black crystals are edenite, then they're edenite.

Yes, edenite is found in Bavaria:

https://www.mindat.org/min-1351.html

No, edenite does not form in water (under anything remotely near STP conditions). It requires significant heat (hundreds of degrees celcius) to form. It is not a precipitate of aqueous solutions. You're just as likely to have diamonds and emeralds start precipitating out in your tank as a hornblende mineral.

I'm not sure why you're still researching this now that you got test results back. Twice. Saying the same thing.

[Andy Love]

[Andy Love]

[Pete Richards]

Hello Andy,

Though I am a moderator on this forum, I am writing this response as myself, an individual. I have Master's Degree level training in mineralogy, and have studied minerals for 35 years post PhD. That does not mean that I know everything, but it does at least indicate that I have been introduced to current thinking from many professional mineralogists and petrologists.

You express some frustration that you have not heard more from us, and some sense that your posts are no longer welcome. I will say that I have found this an interesting thread, exactly because of your tenacity in pursuing your mystery and your ideas about how to understand it. You have done a lot of work and spent some money seeking answers. At the same time, this thread is frustrating because many of us are telling you that your hypotheses about minerals forming in your fish tank are totally in conflict with the large body of knowledge about the conditions in which specific minerals form (or are altered into others such as clay minerals). And, having formed your hypothesis, your are determined to prove it.

The best science forms hypotheses, and then improves their credibility by trying to prove them false. Scientists are often unpopular people, because our first response is always "How do you know?!!!"

You have had two determinations that your dark mineral is an amphibole of the hornblende group. It really does not matter exactly what its chemical composition is (which will determine whether it is edenite, fluorrichterite, hornblende, or some other species). All of these minerals form at temperatures of about 550° C to 800° C and pressures corresponding to being buried in the earth at depths of 7.5 to 50 kilometers. Not your typical fish tank environment! This information is based on numerous experiments where rock-forming elements have been sealed in inert containers and heated to specific temperatures and pressures to see what minerals would form. You can search the web for "amphibole phase diagrams" and find the ones I am referencing here (along with many that are irrelevant for this topic).

You propose several "facts" to support your case:

"The black crystals were not present in the raw material from which the aquarium gravel was manufactured : fact."
Or perhaps they like all of the other grains were coated with a white coat to make them appear homogeneous. That is the way my aquarium gravel appears to be prepared.

"The black crystals were not present in or among the gravel grains subsequent to manufacture : fact."
This is essentially the same assertion. It hangs on whether you really saw what was inside the white gravel, and what the manufacturer chose to tell you about their possibly quite proprietary raw material.

"I did not introduce the black crystals to the aquarium gravel before it was added to the aquarium, or before the aquarium was commissioned : fact."
I believe this. But it provides no evidence that they grew in the gravel as you assert, unless it can be shown that you DID introduce them and they have grown larger.

"The black crystals were not present in the planting medium that underlaid the aquarium gravel : fact."
Possibly true, and probably true based on the medium's function, but you have done little to address this question, based on the posts I have seen. So it is an unevaluatable assertion.

So where are we? You have a "remarkable" observation of a hornblende mineral growing in your fish tank, and attribute it to something going on in your tank. The huge body of experimental petrology indicates that this is impossible. How can you proceed? I think spending time/money on identifying the particular amphibole species is a waste - it will gain you nothing.

If you really believe your fish tank grows amphiobles and micas, do some further controlled experiments. Get fish gravel from several sources (perhaps including local stream gravel, screened to the right size and sterilized). Make epoxy-embedded mounts of each source, and have thin sections made (for a cost) to see what minerals are really in there. Set up tanks innoculated with the same water and with each source gravel, and run them for however many months or years (another variable). Then wash the gravel, make new epoxy mounts, and see if you can document statistically that the amount of amphibole or mica has increased over this time. Can a replicate tank produce amphiboles? Do other tanks also do so?

If you can provide this experimental evidence, we might take you more seriously. But for the moment you appear to be someone who has an interesting but unplausible hypothesis that the body of scientific evidence does not support, but that you are determined to advance.

The length of the message will convey, I hope, that I am not hostile to your postings, but that I think you are barking up a non-existing tree, and are rather stubbornly refusing to accept indications of that fact.

Until you provide much more substantial experimental and observational reports, I will not respond further.

[Andy Love]

Thank you, Pete, for your considered reply. I understand your stance with respect to the status quo and/or your knowledge-peers ; nevertheless I cannot at this time bring myself to accept it. The possibility strongly seems to exist that I may have stumbled upon something quite unexpected. I know that, as you said, you won't respond to the following ; but anyway ...

The only doubt you raised was the one of whether or not the manufacturer of the substrate was being mendacious for reasons of commercial interest. It's not something that had occurred to my trusting nature, so thanks for that. I shall of course check this out so far as I am able.

I'm not going to waste any more of your, or threadmates' time here. However in the, (unlikely, I know!) event that anyone would like to follow any progress that I might make - maybe also to offer further guidance - I invite them to PM me and I will provide contact details. Prior to de-registering (etc.) I will remain a Member, if allowed, for 48 hours to allow time for this to happen.

Otherwise I would genuinely like to thank you all for your attentions and wish everyone all the best.


A final allegorical offering (perhaps not perfect but at least it's contemporary!) ...

6mA. Who knew, eh? ;-)

[Mike Wood]

I'm quite a fan of 'the simple explanation', generally speaking, as an answer to a lot of life's problems. Maybe someone dropped some 'gravel' in your aquarium for a joke... Have you considered foul play? It would make much more sense to me. (Not joking!)