I was thinking of buying a densimeter to measure gold karat. Most of
them would be scrap jewellery.
Is it accurate?
Is it worth the money? (Around $800 USD)
When and where does it fail?
Are there any other assaying methods that you could suggest?
I was going for the Aqua Regia with touchstone assaying method, but
the fumes from this method is just too dangerous for my working
There are hand held devices that use either a spark or radiation to
generate a spectrum that is analysed to determine the composition of
precious metal alloys (and other metals if you have the suitable
reference library-generally software derived) I dont know how much
they cost though, the spark generating machine is less sensitive than
the xray detector but undoubtedly cheaper. There are several of the
XRF machines on the market so there must be one that is affordable
and will beat a densimiter hands down for accuracy and wont be fooled
by gold plated tungsten bars!
I think you are referring to XRF handheld scanners they cost like
$15,000 and above. I think that is too much for me.
a drop of test acid shouldn't be "too much" for any well ventilated
studio- if you need to install a muffin fan on the bench or area
where you test and draw the fumes away from you. As for a
densimeter- it would be a waste of money compared to some electronic
"pen" type testers out ther. With all the inexperienced people buying
gold staying a step ahead of those selling gold and silver requires a
good eye for plateing jobs or cores of other metal being covered by a
layer of gold, or even silver (there is a lot of fake Tiffany & Co.
NY jewelry coming from China that is plated but the weight is a dead
giveaway. Easier yet is to learn to test the weight of gold and other
precious metals- weight doesn't lie when used with a good stoning.
XRF testing is the best way to go and used units are generally sold
because something went wrong (never buy one off of an online auction
site unless there is a good warranty and return terms on the
purchase). If you are buyng a lot of gold, it is worth the cost of
the 6-8 oz. of gold as an investment. In terms of buying gold and
other metals most pawn stores and coin dealers only pay a fraction
(less than 50%) of spot to the seller unless the seller is a jeweler
or metalsmith, if not another dealer bringing in at least 100 dwt. of
gold or Pt at a time for a 98% of spot payment. refiners or dealers
dealing with refiners send in so much gold, etc. in a shipment that
even paying out 98% to a dealer they make money from the refiner that
they have an agreement with - weekly. So the small drop of nitric
acid containing aqua regia you use to test the purity of an item is
very insignificant in the long run, however learning to read it
correctly requires experience. and not holding it directly under your
head helps tremendously as most people lean over the stone to read
the result. so a small fan is the cheapest way to go if you aren't
using any other methods of testing to make sure what you are buying
is what the seller represents or believes it to be- in most cases the
general public hasn't a clue what the markings particularly on
European jewelry (i. e 875, 816, 666, 550, 523 etc.) indicate so
learning those values, and what to look for in faked pieces is an
important skill to have before you put any acid to the stone. rer