[meteorite-list] Storage of Meteorites - VCI Pads vs. Desicants

From: Mark Grossman <markig_at_meteoritecentral.com>
Date: Sun, 21 Jan 2007 04:31:57 -0500
Message-ID: <001d01c73d3e$ff103f30$6701a8c0_at_QED>

I'm a new collector and could use some advice on storing meteorite samples.

If some of the questions that I am asking have been covered before, I apologize in advance. If so, perhaps you could just e-mail me directly to avoid repeating what may have been said in the past.

What is the group's opinion of using VCI pads vs. desiccant for meteorite storage? I have obtained differing opinions from a couple of collectors. I've seen some glass domes advertised that state that the VCI pad can be hidden behind the label holder in the dome, and that the VCI pad can last for 1 to 2 years. However, there is a caution about handling a specimen that has been exposed to a VCI pad, and I'm not clear on the reasons.

I have also heard that VCI pads can be placed underneath Riker mounts or plastic boxes and that the vapor will go through the support material and prevent the sampling from corroding. Is this true?

I assume the desiccant should be silica gel or molecular sieve material.

I know there are desiccant packs that are sold that I think have calcium chloride mixed into them. When the color changes pink due to moisture, it's time to change the pack.

I have heard that any desiccant with calcium chloride should be avoided. Is this true? Explanations I have heard include migration of calcium or chloride ions from the desiccant into the air of the storage container, which can promote corrosion. I know chloride can promote corrosion. However, the vapor pressure of calcium or chloride ions from the desicant should be very, very low, so I am not sure if that is the explanation.

I have heard some collectors say that except for real rusters, they do not use any air tight containers because moisture is trapped in the container.

What about membrane boxes - are they OK for samples that might be friable or have the potential to fragment with light handling? Will the membrane boxes promote corrosion? How are fragile or friable samples normally stored?

So, whatever tips you can pass on to a new collector would be greatly appreciated - VCI vs. desiccant, air tight container vs. non-air tight container, etc.

The samples I want to store include an Imilac pallasite, a Gibeon iron, a nice H5 chondrite, and a H5 chondrite that is already somewhat rusted due to prior storage in moist conditions. I tend to be conservative, so if advisable, I would probably like to store all of the samples in an air tight box with a desiccant and/or a VCI pad, if that makes sense.

Sorry for the long post, and appreciate whatever guidance you can offer.

Thanks.

Mark

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Received on Sun 21 Jan 2007 04:31:57 AM PST