Featured Chinese mark on white metal, diamonds and jade butterfly brooch

Ha, Komokwa... anyway better than "damaged costume brooch"

 

It is worth buying a testing kit which includes a platinum tester bottle.
I'd be happy with white gold.
Seeing you bought it in a costume jewellery lot, !
I agree, the stones do not look like malachite. But they could be dyed. How translucent are they, and what do they look like against the light?

 

AJ, I'll seek for a testing kit as complete as possible available for shipping to France...
I took pics with a strong light through the pierced window at the back of the mount, very difficult to focus

 

Jade has a messy structure. Through a loupe you can see tiny crinkled thread-like structures, a bit like when you pull a thread from a woollen jumper.
I think your stones are either aventurine or 'Malaysia jade'. Malaysia jade is nor jade but dyed quartz, and often used in Chinese jewellery.
Aventurine is the more likely candidate. We usually associate aventurine with those little sparkles in the stone, but not all aventurine has that. Both stones are 7 on the Mohs scale, just like jadeite jade. But jade is much denser.
Here is info on aventurine:
https://www.gemrockauctions.com/auctions/aventurine/aventurine-gemstones/

The diamonds could also be topaz or white sapphire, both beautiful gemstones.
White gold is usually an alloy of gold, palladium and other metals, as khl said. Palladium or nickel are added to achieve that white colour. Palladium is a precious metal, the price is comparable to platinum. Palladium can have that rhodium look, rhodium is also a precious metal.
No matter what the stones are, it is a lovely butterfly. And since you bought it as costume jewellery, I think you did very well.

 

AJ, I agree it could be another stone, if it was a bead, I'd would be sure! I really don't want to take it apart again... the plaque is under 1mm thick...
Will test the metal when I'll get a test kit and post the result.
Thanks for all your suggestions!

 

No matter what, it's a score!

 

I just get the puritest kit,

I made two scratches on the testing stone.

Tried the platinum testing acid on the bottom one, no modification after 30 seconds.(difficult to get it in pic, but obvious in reality...)

Tried the 14k acid on the upper one, it disappeared fast!

What to think of the difference, could it be another metal?

 

Maybe the wrong solutions in the wrong bottles? Can you test other jewellery, that you know to be 14k and platinum, just to check?