[Nhcoll-l] about preservation of halite minerals in an antique colleciton

[Robert Waller]

Hi Gönenç,
Halite dissolves spontaneously (deliquesces) at relative humidity of 75% or higher. Halite is unusual in that 75% limit holds regardless of temperature.
I don’t think escaping fluid inclusions could be responsible, if for no other reason, that the fluid would already be saturated with NaCl.
In my experience, the most likely cause is that a higher than normal RH was caused by placing a washed but not completely dried specimen or material into the case causing a temporary high RH situation. There may be other reasons but that is the first scenario that I would seek to eliminate as a possibility.
Best,
Rob


Robert Waller, PhD, CAPC, FIIC
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From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> On Behalf Of gönenç göçmengil
Sent: Friday, August 27, 2021 6:17 AM
To: nhcoll-l at mailman.yale.edu
Subject: [Nhcoll-l] about preservation of halite minerals in an antique colleciton

Dear all,

A couple of years ago, I handled the curation of an old mineral collection in Istanbul Turkey. Minerals are exhibited in a semi-closed exhibition area on the ground covered with thick glass. 2-3 years later after the establishment of the collection (some specimens collected around 1890-the 1900s), one of the big halite samples getting started dissolved suddenly. There is no indication of interaction with a fluid, the humidity level is fixed around 70% and temperature around 20-22 °C, I suspect maybe it contains some fluid inclusions and after a while, they dissolved? or NaCl character is not suitable for that microclimate conditions? Did anyone experience a similar problem before?

with my best wishes

Gönenç Göçmengil (PhD in geology)
Istanbul Metropolitan Municipality, Projects Departments
Istanbul, Turkey.


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