Catch all thread - talk or better yet show us

[voce]

Thanks for the reply.

I did look into it, and it appears that there aren't synthetic demantoids. It's easily picked up by a small rare earth magnet, which should rule out a lot of substitutes like YAG. Also the certificate indicated anomalous double refraction, which in an isotropic mineral is an indicator of metamorphic shear stress. With that and the gemologist not suggesting otherwise, I'm pretty sure it's real.

Are there other factors a person should look out for with colored stones? I'm a geoscientist by training so I should be able to understand even a technical explanation, but I know nothing about what makes gems valuable to worthless besides the "4 C's".

It sounds like you picked up a great deal. Sometimes people selling them don't know what gems are worth. However--I wouldn't trust the certificate too much, since it might be faked. In some countries labs can be bribed to issue reports stating gems/jewelry is authentic. Or, if it's a less reputable lab, it could just be that the lab had gotten it wrong. According to Wikipedia, for example, demantoid garnet is "Single Refractive", so if your gem is doubly refractive it's not a demantoid. I trust this information is correct, because AJS Gems, a reliable vendor, has this:
https://www.ajsgem.com/articles/gemstone-refractive-index-definitive-guide.html

If you were to show me that picture of the gem and have me guess, I would not have guessed demantoid. I would have thought tourmaline.

https://www.ajsgem.com/articles/russian-demantoid-garnet.html
If you Google demantoid garnet, you'll see a ton of pictures of demantoid, all of which look different than the stone that you posted.

Specific to demantoids, they typically exhibit some horsetail inclusions under magnification. I would suggest you check out your gem yourself for specific gravity, refractivity, and horsetail inclusions under 30x magnification.

What makes gems more valuable or less valuable really varies depending on which colored stone it is. I recommend Richard Wise's book Secrets of the Gem Trade, as he writes about the qualities gem dealers look for, for each different type of gemstone. From that book, I also learned that most colored gemstones are doubly refractive, including tourmaline. If it's tourmaline, you still have got yourself a great deal, since your gemstone looks clean and vibrant.

 

[aporia]

It sounds like you picked up a great deal. Sometimes people selling them don't know what gems are worth. However--I wouldn't trust the certificate too much, since it might be faked. In some countries labs can be bribed to issue reports stating gems/jewelry is authentic. Or, if it's a less reputable lab, it could just be that the lab had gotten it wrong. According to Wikipedia, for example, demantoid garnet is "Single Refractive", so if your gem is doubly refractive it's not a demantoid. I trust this information is correct, because AJS Gems, a reliable vendor, has this:
https://www.ajsgem.com/articles/gemstone-refractive-index-definitive-guide.html

If you were to show me that picture of the gem and have me guess, I would not have guessed demantoid. I would have thought tourmaline.

https://www.ajsgem.com/articles/russian-demantoid-garnet.html
If you Google demantoid garnet, you'll see a ton of pictures of demantoid, all of which look different than the stone that you posted.

Specific to demantoids, they typically exhibit some horsetail inclusions under magnification. I would suggest you check out your gem yourself for specific gravity, refractivity, and horsetail inclusions under 30x magnification.

What makes gems more valuable or less valuable really varies depending on which colored stone it is. I recommend Richard Wise's book Secrets of the Gem Trade, as he writes about the qualities gem dealers look for, for each different type of gemstone. From that book, I also learned that most colored gemstones are doubly refractive, including tourmaline. If it's tourmaline, you still have got yourself a great deal, since your gemstone looks clean and vibrant.

Thanks for the book reference. I'll be sure to check it out. I'm used to seeing minerals in a certain light, for what they tell us about the earth, or their unusual chemistry, etc. But trying to learn about this is making me appreciate gems for their intrinsic beauty as well. I think I'm on my way to becoming and enthusiast.

The gem isn't mine anymore; the gift has already been given. But if there's a chance of it being reasonably valuable, the recipient will probably try again to get it checked out. You're absolutely right that the reactive index will be a dead giveaway if it is in fact demantoid.

Also, just in the "fyi" category - even normally singly refractive (isotropic) minerals can display double refraction. In the geoscience world we call this stress birefringence, since the cause usually is deformation of the crystal lattice under extreme pressure. It's my understanding the gem world refers to this as anomalous double refraction. I remembering seeing a paper a while back indicating it's not uncommon in garnets.

Incidentally, the cause of radiating inclusions in tough metamorphic minerals like garnets can be extreme shearing pressure. The less resistive minerals deform plastically and flow around the garnet, spinning it over time even as it continues to grow. The spinning garnet traps straight-growing minerals like crystotile in a radiating pattern. At least, that's my understanding. This isn't my area of specialization.

 

[Rare gem lover]

Coming up ! It’s 5.5 mm and super orange. It’s a spess

Now the painful two week wait.

 

[marionberry]

As from today, I am the very proud owner of these 6mm Oregon sunstone trillions. So hard to capture the schiller ... so gorgeous in person!







From SerendipityGemstones on Etsy.

 

[marionberry]

Okay, my apologies in advance as this is not a coloured gemstone but rather a semi-precious agate, a thin slice of so called iris agate.
But it does have colours when viewed in counter light! (Otherwise it's just clear with slightly opaque bands)
I wonder if earrings would work, if they would give me enough situations to actually display the rainbow of colours.
Do you have a feeling about this, have you heard/seen/used this material before?

Thanks!

 

[Bluegemz]

Okay, my apologies in advance as this is not a coloured gemstone but rather a semi-precious agate, a thin slice of so called iris agate.
But it does have colours when viewed in counter light! (Otherwise it's just clear with slightly opaque bands)
I wonder if earrings would work, if they would give me enough situations to actually display the rainbow of colours.
Do you have a feeling about this, have you heard/seen/used this material before?

Thanks!

That’s so beautiful! It looks like a horizon in early morning. I think earrings would be great. Agate slices have long been used in dangle earrings, often in precious metals because of the beauty of the material. I say go for it. You could also do a pendant to keep it horizontal, maybe backing with metal to get the light reflecting back through the stone.

 

[marionberry]

Thanks! I wonder if a metal backing would suffice to get light in. I was thinking I should try to get it cut vertically into two drop/petal shapes to make into earrings. This is my inspiration (by Jan Daggett Design)!

 

[Deathspi]

Okay, my apologies in advance as this is not a coloured gemstone but rather a semi-precious agate, a thin slice of so called iris agate.
But it does have colours when viewed in counter light! (Otherwise it's just clear with slightly opaque bands)
I wonder if earrings would work, if they would give me enough situations to actually display the rainbow of colours.
Do you have a feeling about this, have you heard/seen/used this material before?

Thanks!

I was just thinking of iris agate the other day, as it’s so beautiful but I’ve yet to acquire any for some reason. Love the colours in yours. Very dreamy and ethereal!

 

[Bluegemz]

Thanks! I wonder if a metal backing would suffice to get light in. I was thinking I should try to get it cut vertically into two drop/petal shapes to make into earrings. This is my inspiration (by Jan Daggett Design)!

Ooh, that’s a great idea! I personally adore agate. It has such a soft glow to it.

 

[ZestfullyBling]

Should be receiving my new amethyst this week. DK is going to add a diamond and make pendant. so excited


5.27 ct 13x8

 

[Gloria27]

Should be receiving my new amethyst this week. DK is going to add a diamond and make pendant. so excited


5.27 ct 13x8

WOW, what a cut!
Colour is perfect also.

I am dreaming of a long gem like this to set E-W on a chain, held from upper corners.

 

[marionberry]

DK is going to add a diamond and make pendant.

Wow!Super curious to see the setting for this one!

 

[MJO]

Thanks for the book reference. I'll be sure to check it out. I'm used to seeing minerals in a certain light, for what they tell us about the earth, or their unusual chemistry, etc. But trying to learn about this is making me appreciate gems for their intrinsic beauty as well. I think I'm on my way to becoming and enthusiast.

The gem isn't mine anymore; the gift has already been given. But if there's a chance of it being reasonably valuable, the recipient will probably try again to get it checked out. You're absolutely right that the reactive index will be a dead giveaway if it is in fact demantoid.

Also, just in the "fyi" category - even normally singly refractive (isotropic) minerals can display double refraction. In the geoscience world we call this stress birefringence, since the cause usually is deformation of the crystal lattice under extreme pressure. It's my understanding the gem world refers to this as anomalous double refraction. I remembering seeing a paper a while back indicating it's not uncommon in garnets.

Incidentally, the cause of radiating inclusions in tough metamorphic minerals like garnets can be extreme shearing pressure. The less resistive minerals deform plastically and flow around the garnet, spinning it over time even as it continues to grow. The spinning garnet traps straight-growing minerals like crystotile in a radiating pattern. At least, that's my understanding. This isn't my area of specialization.

The first thing I would do is get the refractive index of the stone using a refractometer. Each gemstone has a specific range of RI that they fall into.

 

[ilovegemstones]

I love the iris agate Marionberry! I just read this about iris agate so I would go with an open back:

The rainbow colors are seen in transmitted light so this stone must be mounted open backed in order to let the light through. The effect is best when viewed in a dimly lit room with the stone between you and a point source of light.

 

[Rubybrick]

Got these back, and the ones with dark inclusions switched. I am so so thrilled.

But I can’t decide on how to set theses. I was thinking just a chain of simple bezel dangles. But I am also wanting to go with hexagons with milgrain. In 18k YG, would that be too “fancy”? What would you choose? Other suggestions?

 

[voce]

Got these back, and the ones with dark inclusions switched. I am so so thrilled.

But I can’t decide on how to set theses. I was thinking just a chain of simple bezel dangles. But I am also wanting to go with hexagons with milgrain. In 18k YG, would that be too “fancy”? What would you choose? Other suggestions?

Simple round bezels, I'd go with a simple, straight design.

Hexagons, I would try to give the design a twist, like zig zags.

That's a beautiful set of emeralds. Can't wait to see it set

 

[marionberry]

I adore yellow 18k with emeralds. So classy and not too fancy at all. I'd probably want to do a hinged construction as I am obsessed with hinged gold jewellery and I love the fluidity of movement when worn.

 

[ZestfullyBling]

My not so perfect 3.63ct aqua DREAM!

 

[ZestfullyBling]

The aqua will be part of my pendant design with the amethyst
my inspiration photos

 

[mellowyellowgirl]

Calling gem gurus

https://www.etsy.com/au/listing/609...t-pink-sapphire-loose?ref=shop_home_active_69

Does this seem very overpriced? I paid a lot less for a bigger one. Mine is not orange though. Is the orange making it more expensive?

 

[Rare gem lover]

Calling gem gurus

https://www.etsy.com/au/listing/609...t-pink-sapphire-loose?ref=shop_home_active_69

Does this seem very overpriced? I paid a lot less for a bigger one. Mine is not orange though. Is the orange making it more expensive?

Most likely it’s more expensive just because it’s one of her best. I’d say it is overpriced. But orange make make it more bright maybe? Don’t think that increases the value but for some people it may increase the appeal.

 

[Rare gem lover]

I have this Umbalite incoming. It’s supposed to be more purple than red. I do love the mix though. It’s a great size and cut so fingers crossed I get to keep it

 

[mellowyellowgirl]

Most likely it’s more expensive just because it’s one of her best. I’d say it is overpriced. But orange make make it more bright maybe? Don’t think that increases the value but for some people it may increase the appeal.

I was wondering if the orange pushed it to pad territory hence the price.

 

[ChanterelleJ]

I guess it's expensive for the *hot* pink. Seems to be a vivid pink indeed and vivid never comes cheap. I do not see much orange but that could be the pictures.

 

[qubitasaurus]

Calling gem gurus

https://www.etsy.com/au/listing/609...t-pink-sapphire-loose?ref=shop_home_active_69

Does this seem very overpriced? I paid a lot less for a bigger one. Mine is not orange though. Is the orange making it more expensive?

I see a lot of purple in it and some half-and-half extinction, so not a fan for the price. I think this one is more hot pink

https://rogerdery.com/gems/hot-pink-sapphire-rectangular-cushion-1801013/

 

[mellowyellowgirl]

I see a lot of purple in it and some half-and-half extinction, so not a fan for the price. I think this one is more hot pink

https://rogerdery.com/gems/hot-pink-sapphire-rectangular-cushion-1801013/

Ohhh I would love to know how much that is! But not buying one so can't be a nuisance and ask!

Is the stone I posted precision cut? Would that affect the price?

I can tell the obvious native cuts but some of the precision cut's I'm not sure it it's not obvious!

***

On another note I hope to post and learn about stones in this thread. I hope you guys who know what you're doing all chime in!

 

[qubitasaurus]

Ohhh I would love to know how much that is! But not buying one so can't be a nuisance and ask!

Is the stone I posted precision cut? Would that affect the price?

I can tell the obvious native cuts but some of the precision cut's I'm not sure it it's not obvious!

***

On another note I hope to post and learn about stones in this thread. I hope you guys who know what you're doing all chime in!

I would welcome input from someone experianced at fasceting. Precision cutting is quite strict, it will require exact angles and all the meetpoints should match up (the hand shot makes it appear like they dont). If you are looking for high performance light return, then I suspect you'll be bothered by the (dark) line of destructive interferance in the middle, and maybe the silk (to me the silk looks signifcant enough to impact the sparkle -- although this may also be helping improve the glow/strong colouration).

I have found yvonne's photos rather reliable for colour. I suspect it really does look like this, and thus if you really like the colour then it probably wont disapoint. I just prefer the colour of the roger dery stone, but colour preference is very personal.

 

[Rare gem lover]

Ridiculously blue aquamarine coming through! Perfect Clean round brilliant. Can’t wait to see it in person

 

[Rare gem lover]

Ridiculously blue aquamarine coming through! Perfect Clean round brilliant. Can’t wait to see it in person

Better pic

 

[leslie1956]

Better pic

Beautiful, vivid aqua, Rare gem lover!