[meteorite-list] Ghubara as a bleeder

[Adam Hupe]

The important thing with Ghubara is the same for most chondrites. It is all 
in how it was prepared. Any known bleeder like Ghubara should be polished to 
a lustrous finish regardless of contrast lost. The more polished a surface, 
the less surface area available to trap moisture.  It is important to polish 
both sides of a chondrite slice immediately  after it has been cut for this 
very reason unless it was cut using mineral oil in which case until it dries 
out.  Never polish with tap water which starts a reaction in some stones. 
Always use distilled water which is cheap and better on the polishing 
equipment. Chlorine and other chemicals contained in tap water are 
corrosive, especially in contact with metal.  It also attacks the rubber 
seals and bearings in your cutting and polishing equipment.  It is important 
to clean a slice immediately after polishing and to heat it up to no more 
than 190 degrees Fahrenheit for about an hour. Anything higher than 190 
degrees may drive off some of the extraterrestrial gases contained in the 
meteorite thus invalidating some future scientific study.  If oxidation 
appears in the future, dry polish it using emery cloth and wipe it off with 
a lint-free towel. I have had to dry polish two or three times with some 
real troublesome stones until they equalized with their environment and then 
never had a problem again including Ghubara.

Hope this helps,

Adam