Featured Is this red corol stone?

If you think it's glass, then the definitive is lemon juice.

 

The purpose of lemon juice is a reaction with the calcium in the coral, it bubbles. Do it at the back.
Or leave it in milk for a couple of hours, red coral will colour the milk.
But my favourite is simply a more detailed picture of the stone, no risks involved. Just place it on a white piece of paper and take a picture close enough so we can see if there are lines in the coral, or other details.
It doesn't have to be glass though, I am thinking an early plastic.

 

Highly unlikely to be early plastic with that 19th C pin back. 19th C plastics couldn't simulate that colour for one thing, and in any it would have degraded and shown signs of that. Many early plastics were unstable in the long term and get stinky and sticky with age orcrack.

The lemon juice reaction is with calcium carbonate, not pure calcium. That's what coral is mainly composed of - CaCo3. Classic acid/base reaction.

The milk thing, if ever it works, is down to light refraction rather than alteration of the milk colour. Milk is almost ph neutral so can't react as such. Bit like the UV on amber test - refraction.

Anyone got a spectrometer lying around?

Ah. Actually, that's a thought - if you've a diamond tester, see if it shows as glass hardness or if it's a bit more.

 

You're right calcium carbonate, I was just about to add it, but you beat me to it.

Personally I never use any invasive testing on coral, that is why I said my favourite is simply a more detailed picture. Diamond tester is ok, if you can't see any coral characteristics.

If you read my post correctly, I wasn't talking about the brooch but about the bracelet. I also wrote that though made in the same style, I thought the brooch is coral.

On early plastics, here is a detail of my Art Nouveau pendant with celluloid face again. Very 19th century. Doesn't stink, stick, or crack. None of my early plastic jewellery does.

 

That's because it's casein.

 

Interesting, because casein based plastic was invented in the 1890's after this necklace was made (bought 1890). A casein plastic avant-la-lettre?
Just rubbed it, smells like camphor. Celluloid it is. Casein stinks, especially to a lactose-intolerant like myself.

 

Do you have categoric proof of purchase, then? I presume you've done the stink thing.

Anyhow, reverting to the subject, the cameo isn't plastic given it's in a late 19th or very very early 20th C setting pinback.

 

As I already wrote, I did 'the stink thing'. I repeat, camphor.

The bracelet, which is all I have been talking about regarding it not being coral, does not have a pin. As I clearly wrote several times, I think the brooch is coral, not molded.
I thought we could at least agree on the fact that bracelets don't have brooch pins.

 

i love a spirited debate......!
a dozen roses for you , both !!!

 

Thanks Komo, don't know about Obb, but I am very happy with those.
I hope this reply is clear, I seemed to have trouble getting through earlier on in this thread. Do tell me if I have to explain.

 

It's a set. No reason to be different.

Best I change a few settings.

 

Here is a simple test for glass vs. plastic. Tap the piece on your front teeth, then tap a know piece of plastic and a known piece of glass, you can really tell the difference

 

There is another way to distinguish real from fake. No 2 carved cameos are ever completely alike, not even the same subject in the same material by the same hand. If any 2 are absolutely identical, line for line, then, no matter how convincing as coral, they have to be molded.

Between the bracelet & the cameo brooch (think we all agree the cabochons in the other brooch are glass) there are 6 cameos. While the smaller flanking ones have similarities - there is a pair that are mirror images of each other; & there are the 2 with a crown of flowers that are basically the same - no 2 are identical. The 2 center cameos are quite different from each other. Makers of artificial cameos do not go to all this trouble. They may have a few designs, sometimes a right & a left facing version of a profile, but not a stockpile of all different ones.

I was not comfortable with the color as it appears in some picture, so prepared some photos of a few artificial pieces for comparison.



The material of the largest one has a weird optical property. To the eye, it is the same color as the one on its right; the camera sees it differently. The most sophisticated finding on any of them is the safety clasp on the largest one. The third photo shows the 'undercutting' on that one.

Most red coral has been dyed, & some color will wash out when soaked, even in plain water. I'm sure that milk would turn pink I have persuaded myself that the bracelet & companion brooch are genuine coral. Here come the counter arguments.

The smallest cameo in my artificial threesome is made of Celluloid or something very similar. Celluloid has been around for quite some time:

https://www.chemheritage.org/distillations/magazine/celluloid-the-eternal-substitute