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Message: <blockquote data-quote="Ancalagon" data-source="post: 7130211" data-attributes="member: 23">HelloSo... in my campaign, the characters have a good chance of finding vials of quicksilver as a treasure.  This made me realize that... I don't know how valuable it is!  I think we can all agree that quicksilver would be considered to have significant value... but that's vague.  Is it as valuable as copper?  As gold?  More than gold?  etc etc.I tried again and again to find information on the price of mercury in the middle ages, but to no avail.  However, I have just found a quote from Pliny the Elder"Nothing is more carefully guarded. It is forbidden to break up or refine the cinnabar on the spot. They send it to Rome in its natural condition, under seal, to the extent of some ten thousand pounds a year. The sales price is fixed by law to keep it from becoming impossibly expensive, and the price fixed is seventy sesterces a pound."Ok, so the price of cinnabar - an ore of mercury with the formula of HgS, is 70 sesterces a pound.First, some roman unit conversions.  1 roman pound = 328.9 grams, so cinnabar is 96.6 sesterces an imperial pound.The value of the sesterce varies, but I believe that around the time of Pliny it was worth 1/4 of a denarius, which is a common silver coin (3.9 grams/coin).  So 1 imperial pound of cinnabar = 24.2 silver pieces.All right!  but what about quicksilver... Well here we have to do some fiddling.1:  Purity:  I'm going to assume that this ore isn't completely pure since it's in natural condition, but that also it's not garbage, so 75% pure2:  Processing efficiency.  This is is a wild guess, but I'm going to assume that the process is 50% efficient - there are some losses due to evaporation of mercury and other errors.3: Processing cost:  this is a reflection of the cost of refining the cinnabar into mercury.  Alchemists and retorts aren't cheap (see <a href="https://en.wikipedia.org/wiki/Cinnabar#/media/File:Alchimia_1570_p_9.tif" target="_blank">Cinnabar - Wikipedia</a> for a neat illustration).  I'm going to say this doubles the cost4:  Amount of mercury in cinnabar:  ah well this one we have exact numbers based on atomic weight and the HgS formulae:  200.6/232.6, or 86%   This is not the same as #1, that was for pieces of rocks etc.So the cost of a pound of quicksilver is:  (24.2 X 2)/(0.86 X 0.5 X 0.75) = 150.1 silver pieces (for pieces of silver of 3.9 grams).This means that quicksilver is roughly 1.5 as valuable as silver by weight, which makes it fairly precious, but not insanely so.(edit:  I made this into a blog post <a href="https://slugsandsilver.blogspot.com/2019/03/on-value-of-mercury.html" target="_blank">Price of mercury in D&D</a> )</blockquote>

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