It's not onyx....I am thinking coal...?
Is there any metal on it? perhaps some very tarnished silver?
Also thinking mourning jewelry?
I'll do some research and see what I find....

The only metal is the clasp and hook on the back. No it's not tarnished and it is to hard for coal. I will be anxious to see if you come up with something.

I think what you have is something like this.....really quite rare.
Where did your great grandmother live? near coal mining areas?
Linda c

Here is a link that might be useful: Victorian carved coal

OOh interesting! It really doesn't look like onyx. I was thinking maybe ebony but looking at the coal stuff, I think Linda has it. Google "Whitby jet mourning brooch" images. It's really very nice compared to others--and not terribly depressing like some of them.

It is probably "jet" or lignite
http://en.wikipedia.org/wiki/Jet_%28lignite%29

I like the bird and nest motif.

I think Linda had it right on mourning jewelry. The only prerequisite for that was simple and usually black and it was used at least up until the first world war. It may be onyx, but I also think it is likely jet. Jet was not usually polished for mourning jewelry. There is a tremendous difference between the hardness of onyx and jet and any jeweler should be able to verify which it is, and so you could as well but it would mean scratching it, and you may not want to do that. To the touch coal does feel hard.......I've heated with enough of it. How can you say it's too hard for coal just by touching it?

Very interesting...Here's one of Civil War era that looks a lot like yours and apparently made of hardened sap-like rubber from a certain tree:

http://www.worthpoint.com/worthopedia/rare-antique-authentic-gutta-percha-mourning

Wow, this is so interesting. I only guessed that it would be to hard for coal, but I have never heard of carving anything in coal. I need to ask my dad about this and see if he has anymore information. The examples that you lead me to in the links above sure look like that is what it is. I may have to take it to a jewelry shop and have them look at it. Are they worth anything? Should I insure it?

Chloe........never knew gutta percha was used in jewelry making. Thanks for the link. I started reading up on jewelry made of it, and I found the remark that gutta percha jewelry was usually moulded and not carved (makes sense since it starts out as latex, doesn't it and would be liquid at one point).

Even though the photos the OP posted are excellent, I certainly can't tell if it were carved or not.

Doris........not saying your family doesn't know what they are talking about....LOL. What I am saying is I do genealogical research and even though I do not discount oral history I have found out that alls it takes is one person along the line to make presumptions and repeat them to the next generation, and it's usually accepted as absolute fact whether it is or not. Is it valuable? I dunno in a monetary sense. For one thing, it depends on the material of which it's made. Then one has to consider the antique value on it. Even bakelite plastic jewelry now is very pricey. So you may not be able to get the complete story from a jeweler. They know their gems, but may not know antiques.

If you google prices on old gutta percha and jet jewelry........you can find similar items from ten dollars to hundreds of dollars. If you have numerous items like you said.........you may need to get appraisals on all of them (not just opinions from any of us, regardless of how accurate we may or may not be) and then get a rider on your insurance for the kit and caboodle of them. That's what I did.

Apparently, gutta percha started being used as a much less costly substitute for jet, when jet could no longer be mined in England. I enjoyed learning about this. Thanks for posting your lovely brooch!

I was thinking Jet also, since i'm not too experienced with Victorian jewelry, and didn't know coal was actually used. I worked with a woman who collected jewelry of that era, and know she had pieces that were Jet.

Here is a link that might be useful: Jet Brooch

I believe that I forgot to mention that it is hand carved. I think someone asked about that earlier, and I didn't respond to it. Thanks for all the input. I have learned so much.

It looks like jet to me too, but it is hard to tell from a picture. Jet jewelery and mourning items were very popular in the late 1800s, especially in the UK. Jet was mined and carved in Whitby, Yorkshire, and the town became famous for it.

It could be imitation "jet," like the much softer carved coal, or the moulded gutta-percha already mentioned. It could also be moulded glass. Jet is warm to the touch unlike glass, and if the edges are sharp it is more likely to have been carved.

The definitive test is to use a red hot needle on some spot that doesn't show. Jet will smell like burning coal. I don't advise doing that yourself, you might damage or destroy the piece. Jet can burn!

FYI, small quantities of jet are still hand-carved and sold in Whitby, Yorkshire. These days it is hand-gathered not mined, and at least one jeweller reproduces the old designs. The Whitby Museum has some good examples of real antique carved jet if you want to google it. :-)

Keep in mind that there are different kinds of jet and jet substitutes- Whitby Jet being the most collectible.

The imitations are collectible in their own right, but not quite as desired. Consider vulcanite, French jet (which is a fancy name for vauxhall glass), Ebony wood, bog oak, pressed horn, and gutta percha.

This has more of a vulcanite feel to me, as it has a brownish transparency in light.

One way to test is the scent and scratch test. Whitby jet will have a coal-like scent and will leave a blackish residue if you scratch it on cement.

Vulcanite will have more of a sulfuric scent to it and appears lighter in color when compared to whitby jet.

I worked in an antique shop in the 1980's and we sold pieces like that and they were considered Victorian mourning jewelry. You could also consider the site Ruby Lane which sells very high end costume and vintage jewelry for a possible value.