Surely anyone who melts things or heats things (silversmiths, glass fusers, potters/ceramicists etc) has to be a bit of a chemist? There might be more people interested than you would think.
(Althoug it drives me a bit nuts the number of glass fusers who want ready written firing schedules without understanding what each stage is for and therefore what might go wrong or how to vary it to get the required results.)
Murano is an island near Venice where the sensible venitians (Iāve not spelt that right have I) put all the glass workers when they realised that they were a bit of a fire hazard (a lot of the buildings were predominately wood in construction and the glassworkers tended to have fires/ kilns). Any glass made on the island of Murano is murano glass, any glass made elsewhere that looks like the stuff made in Murano is āmurano styleā glass, there are a few big workshops and lots of little ones rather than a single factory on the island and I had great fun poking round the workshops whilst on holiday and listening to the workers complain about how time consuming it is to make some of the beads. Its a bit like champagne which can only be made in a specific bit of France but can be made by several vineyards within that region, anything made elsewhere is champagne style sparkling wine.
Iām probably in a minority, but the use of the word āgenuineā always has me wondering if it really isā¦
I just unearthed a strand of malachite chips from my stash and couldnāt resist testing it. First I tried vinegar and it showed little sign of fizzing - but in warm pickling solution it bubbled away merrily. Then I heated it with a small flame. It did give off some smoke and turned black but didnāt melt. I would expect the residue to dissolve in acid but so far it hasnāt done so! The results are a bit ambiguous but on balance I think itās the real thing - do you agree?
The imitation stuff is based on resin which would melt, blacken and give off smoke when subjected to a flame. The malachite bead I tested with a flame - the material darkened (consistent with the formation of copper oxide), retained its shape and there was no noticeable smoke (wouldnāt have expected to see the CO2 being given off). Sometimes malachite is waxed or oiled to give it a sheen if its not been properly polished, this might be what has happened to your chips giving the smoke on heating. The black discolouration is consistent with the formation of copper oxide like with mine.
Sterling silver contains copper which tends to form the fire stain that gets removed by pickle so if your pickle already has a high concentration of copper ions in it (from being used for its proper purpose rather than a random chemistry experiment) that would slow the rate of dissolution of the copper oxide residue left after burning. The bubbling you saw with the unheated chip in pickle was the formation of CO2 as the carbonate reacted with the acid (the vinegar probably isnāt a strong enough acid to get this reaction to occur quick enough to be visible). I used lime scale remover for my test and got a few bubbles and a nice blue solution (hello copper sulphate).
So weighing up the chemistry I would go with your chips being real malachite.
Iāll add more to that - I havenāt been able to find out what sort of resin does get used for the imitation materials just that it doesnāt react with acid. Iāll keep digging but the type of resin used may vary from factory to factory so there might not be a simple answer for me on that bit.
As a novice at this, I have tested my stash of malachite in vinegar - nothing, no fizzing or bubbles. If I heat it up with a flame and it smokes is that smoke noxious (ie shall I do it outside) and is it a quick process.
Sorry to be a pain but you have āpippedā my interest 
Oh no what have I started. Please be careful. If you have some sort of eye protection then wear it just in case (mine came home with me when I stopped being a chemist along with a lab coat and mini blast shield) and make sure you torch it on a suitable surface. If it is the resin based stuff then yes the smoke wouldnāt be pleasant and you are better off outside, youāll need to find a sheltered spot with no wind or the smoke bit will just get blown away. How quickly it happens will depend on the size of the piece you are torching - start small and it should be quick. I donāt think vinegar is a strong enough acid to get a visible result for that test and something stronger like limescale remover would be better. Again please, please be careful.
lol thank you @SashaGarrett yes I have safety glasses and the torch I am using is onto a heat resistant surface - I promise to be careful.
Iām not a chemist - physics was my subject - but still find it fascinating so donāt think everyone would find it boring. I have a similar problem with silk used in my nuno felting as there is a lot of āsilkā out there that is actually polyester! There is a burn test for it but sometimes if I am using a ready made scarf its not practical - generally though nuno felting only works on real silk ( you can get it to work on polyester but it takes forever) so if it doesnāt work I know Iāve not got the real McCoy!
Back to the original post - might be worth saying in the listing that malachite is often imitated which is why you have tested it which may then avoid the query over whether your other materials are genuine and why they havenāt been tested.
This is an interesting thread , It hadnāt really occured to me that malachite would be imitated, as it used to be a widely available relatively cheap material, and easy to work.
So I had a look at why it has become scarcer. Apparently due to the political unrest and corruption in the Congo - (where there are still tons of the better quality stuff), no one will risk the instability and invest in the mining.So very little is reaching the market now.
Another interesting thing I came across, that I hadnāt questioned before, was that some countries will only export their minerals as finished products rather than rough for cutting, which is why at gem shows you will see huge rough ash trays made of stones, I always thought what a waste of lovely stone, I didnāt realise they were intended for cutting down once exported.
I like your thinking Roz - perhaps stating that malachite is often imitated and that for my own piece of mind I chemically check my material myself to ensure that it is genuine at the bottom of the listing is the way to go. I donāt want to start a movement of home chemists setting fire to their malachite to see what it does.
spoil sport 
Are there any other semi precious stones we can conduct evil experiments on?
If you promise to be careful and wear the appropriate safety gear Iāll tell you how to make your own crackle quartz or agate which is about the only exciting thing you can do with all the silicates at homeā¦
oohhh loving these ālearn with Sashaā sessions 
and crackle quartz sounds wonderful
I have visions of Folksians all over Britain with masks and blow torches 
Fantastic thread Sasha, and i can fully understand you wanting your buyers to know they are getting the real deal, there is so much fake about and listings which will say āRose Quartzā etc but they are just referring to the colour, unless buyers read the listing thoroughly including materials where they will find that the material is in fact stated as resin or clay they think they are getting real quartz.
I will be watching and learning your testing posts with great interest then running into the workshop and performing the tests
The lab created gems and sellers not stating they are lab created ie the main stones emerald, ruby, sapphire, Amethyst etc has been a great bug bear of mine for years as i work with Gems in healing iām mostly only interested in gems that come from the earth (because of their energies) hence my gripe with lab created and before someone brings up CZ and Goldstone yes i know they are glass (lab created)
Itās a shame though that we need to feel that we need to start adding extra info about the stones but can fully understand why.
Having said that it can be a minefield for the buyer too, for instance some of my emeralds Rubies Sapphires are from Jaipur but then would i need to add that they are the main receiver of rough from Zambia and Brazil yet some of my faceted rubies are from burma, i think what iām asking is how much information should we be using to try to explain they are the real deal without overloading them but making them aware they are real and not fake, how do others get around this, and do we need to be asking Folksy for additional page say a blog page
OK Rachel @GreenwoodMakes and Sarah @plainprimitives you get the background about silicates firstā¦ Silicon dioxide (aka silica or SiO2) takes many forms in nature (or glass in your house with a few additives). In its pure form its quartz (or rock crystal) and has an extended (ie large) crystal structre but the fun happens when you start adding impurities or altering the crystal structure. If you add iron (specifically Fe3+ ions) to quartz and irraditate it you get purple amethyst (this does happen in nature as the crystal forms, can also happen in a lab), if you then irradiate the purple amethyst it goes green (green amethyst = prasiolite, again can happen naturally or in a lab) and heating produces yellow quartz (also known (perhaps inaccurately) as citrine but might get labelled congac quartz, lemon quartz etc depending on the hue, the yellow colour is because the Fe3+ ions have turned into the oxide). Some citrine is formed by taking clear quartz and adding aluminium ions but if you add to much or irraditate it (again can happen in nature or in a lab) you get smoky quartz. Differentiating between the lab treated stuff and the natural stuff can be hard and require some fancy kit (polarisable light source and years of experience)). Still with me? Good. So far Iāve been talking about macro crystaline quartz types but you also get micro crystalline quartz (macro = big crystals, micro = little crystals) and these are your agates, jaspers, flint and quartzite amongst others. Here you have tiddly tiny crystals of quartz, potentially with lots of impurities and small crystals of other things, all compacted together bit like a sugar cube. Right my head is hurting from all that so Iāll leave the included quartzs (rose quartz, medusa quartz etc) and crystal polymorphs (opal, chalcedony) for later.
On to the fun bit - thermal shocking your quartz. When you add cold ice cubes to tepid water they expand and crack, to get crackled quartz you do the same sort of thing. Donning your safety glasses (you may also want to find a responsible adult) youāll need to heat up some quartz beads (or agate or plain glass) with a blow torch (on a heat proof mat, outside, away from anything flammable, small children and pets please) and then tip them into a bucket of cold water which should cause them to crack. You need to be really careful when heating as any flaws could cause the bead to explode (safety goggles really are a must for this). The greater the difference in temperature between the quartz and the water the more cracking you should get but if there is too much you run the risk of the bead fragmenting. To add colour to the cracks put some food colouring or other dye in the water - it will slowly seep into the cracks to give a non permanent effect.
Have fun!
Thank you for this, Sasha. I look forward to cracked Quartz popping up all over Folksy!