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[Sifu]

I have some lovely jasper-agate, where the jasper is so iron-rich that a piece I cut 2 years ago (but did not polish) is now showing slight signs of oxidation (rust). The agate is clear to blue. It's awesome looking material, but I'm wondering if I should do anything special to stabilize it once I polish it, and prevent the oxidation. Does anyone have experience with something like this? I can't imagine that polishing will magically prevent future oxidation - does this mean I have to apply some kind of clear coat?

[lithicbeads]

A few stones prone to radical oxidation do not oxidize when polished. In your case  a quartz  cap may work  but coating other than a spray coat is difficult to put on evenly  and polish.

[rocks2dust]

Metal disease (also called Byne's disease or metal cancer) is a generally irreversible reaction once it has started. Processes using ammonia gas or ethanolamine thioglycollate can stop the process, but not repair the damage. These "cures" can cause color changes to the piece and do not prevent recurrence. Metal disease affects a variety of metallic inclusions, including copper and iron-bearing metals such as pyrite/marcasite, chalcopyrite, silver, bronze, etc. Sealing can actually accelerate the process by trapping sulfur, moisture and/or oxygen. You can slow it by cleaning in pure alcohol (no water) to remove loose material. If the damage is very light, you may be able to sand down below the damage and repolish, afterward drying thoroughly and avoiding the things that trigger this type reaction in the first place: keep away from sulphurous substances and air pollution, store only in archival conditions – e.g., not in proximity to PVC and similar plastics, not around acidic wood (including oak/cork and wood-pulp cardboard or papers), not in contact with or in containers containing ordinary cotton, inks, ordinary tapes, glues and paints. You should also immediately wipe off fingerprints and body oils using pure alcohol after wearing/handling, maintain very low humidity with silica gel replaced frequently, isolate from other metals, metal-bearing stones and settings to curb the spread to other pieces.

[tetonartgallery]

Any stone that takes that kind of care to protect it from turning to its natural state is one I would rather not cut no matter how purrity it is. IMHO

[rocks2dust]

I'd agree, except "pretty" can be fairly compelling to me, whether it is marcasite, calcite or similar vulnerable mixes. The other thing is that the corrosion disease problem can also arise in the metals into which stones are set, and both metal-containing stones and settings can last a long time with a bit of caution when storing and wearing. Not all that much different than avoiding storing diamonds, sapphires, emeralds and agates in a big jumble in a bag for storing – a sure recipe for severe scratches – just taking an extra step to avoid storing with acidic materials and high humidity

[tetonartgallery]

good point

[Sifu]

Thanks for the feedback. My first step then will be polishing a test piece and taking a wait and see attitude.