FMF - Friends of Minerals Forum, discussion and message board

[Paul S]

[Tracy]

[alfredo]

Tracy, An electric dehumidifier in the mineral room will work wonders. I bought one on amazon dot com for about $200. Not only protects the minerals, but prevents mold growth and makes you feel more comfortable in summer too, so I consider it one of the best investments I've ever made. Just remember to empty the water bucket every day in summer, or else it switches itself off when the bucket is full.
Regards,
Alfredo

[Tracy]

Thanks Alfredo. I do have a dehumidifier which is connected by hose to the outside (so it never gets full and I don't have to empty the water all the time). The pyrites aren't close to it, though. Maybe I'll relocate them.

- Tracy

[chris]

Hi Tracy,

If your specimens are inside a display, you can also buy a small cartridge dehumidifier as I did and put it inside your display or just beside it (like I did). It will create a small area around the display with much less moisture in the air as a result.

Don't know if it is the consequence or if I'm just lucky, but none of my sulfides every decayed until now.

Christophe

[Pete Modreski]

Tracy,
Out of curiosity, what was the locality of your starting-to-decompose pyrite specimen that led you to begin this thread? As people have noted, pyrite from some localities pretty much "never" decomposes, some occasionally, and some, often.

There have been a number of research studies recently that also show that bacteria play a role in the decomposition--some like to "feed" on minerals, and that introduction of organic materials (skin oil from handling?) can accelerate decomposition, and different types of sterilization may inhibit it.

Pete

[Joan R.]

I've treated some samples of Catalan Baryte specimens from an old mine. These specimens where partially degraded because in the matrix there was sulfides (galena, marcassite, pyrite?) and possible bacteria. I've used Sulphanilamide (CAS 63-74-1), a sulphamide very soluble in acetone. I will inform about results.

[Tracy]

[Tracy]

Here's another related question: what about light-sensitive sulfides (or any other minerals) that exist as inclusions - e.g., realgar in quartz or orpiment in calcite? Will they degrade unless kept out of the light?

- Tracy

[chris]

Hi Tracy,

Just wondered the same as you. Unfortunately I have no answer. But I assume it is closely related to the lightwave(s) that trigger the decay. if the surrounding mineral acts as a filter the mineral could be protected.

Does anybody has realgar included inside calcite in his/her collection which has been exposed to light for some years ?

Thanks

Christophe

[Carles Millan]

[Carles Millan]

A bit more about realgar becoming orpiment...

Not only orpiment has arsenic with a higher oxidation state, as said in my previous message. It has more sulfur (or less arsenic) than realgar. So I can't see how in a tightly closed environment like a quartz inclusion can such process be performed. No matter you irradiate it at any wavelength, it's not possible to increase the sulfur content neither make the arsenic disappear.

[alfredo]

Carles, That was actually an old mineralogical mistake, that realgar alters into orpiment. In reality realgar alters into pararealgar, which has the same As-S ratio, so I don't think any oxidation is involved, just a change in the bonding and crystallography, so it would probably happen even if the realgar were completely isolated as an inclusion in quartz, Baryte, etc.

[Carles Millan]

[Tracy]