This is a Andradite-Grossular garnet I got off someone from etsy. It is a green garnet. It reminds me of Dementoid garnet. I don’t know the difference. But it is not. Does anyone know what the value of this garnet could be? It is about 84 grams. Wherever I sand paper off the brown polished rock it is green gemstone underneath. Thanks
Demantoid is a variety of Andradite, so the green hue could indicate the relation. The brownish-red colored crystal is also typical for the variety. Unfortunately, It is difficult to see true color definition in the images.
Whenever I sand paper off the brown polished rock it is green gemstone underneath.
This seems to indicate the brown is a surface oxidation. What type of sandpaper are you using? Are you applying the sandpaper to the crystal surface or on some of the matrix. Can you point out where you scratched the surface at, please?
It is difficult to assign a value to this crystal without analytical testing. (i.e. Specific Gravity and Spectroscopy are very good tests.)
A good reference for this garnet species is here: 14 Mineral Descriptions – Mineralogy
Oh i have diamond grade sandpaper. It is not actually sandpaper. it is not made of paper. I got it off amazon. Very neat. It cant actually go bad. This was a polished rock to start with with some green gemstone showing already polished to. I was taking off the brown rock matrix around the gemstone. First i got off some polish on the matrix part of the rock. then i was taking off the matrix part of the rock to get to the green gemstone. The gemstone is Not shiny where i sanded it with diamond grade sandpaper was taken off because it the polish is gone. I was sanding the outer brown rock up to the green gemstone. My goal is to keep as much gemstone as their as possible! I could say i sanded the surface where the gemstone looks dull and not super shiny! So in the middle where the gemstone is really shiny green i did not sand paper. That part came when i bought it like that! I would love to put up more better pictures! Also where i was sanding it their were some spots were some rock bits were embeded in the green gemstone. I will put up more pictures soon. Thank you!
It weighed 81.6 grams exactly. Water in the cup weighed 240.2 grams exactly. The weight of the gemstone water in the cup weighed 321.7 grams. Their was too much water in the cup i hope that does not matter! I took 81.6 divided by 240.2 and got .339716902581 irrrational number. I hope im doing this correctly to find the density! Also their is still some polished rock on the matrix of the gemstone. I hope that does not matter! I will try to see if i can try the next test! Thanks!
I just watched a video. I did not know i had to use a string to put it into the water. Ill have to redo the test! Thanks
I was just about to link this YT vid… Specific Gravity Test -Grossular Garnet - YouTube
But it seems you may have figured it out… Looking forward to the test results…
Garnet in grams 81.7. 251.8 rock suppended in water. I got a awnser of density 3.082007343941 irrational number! I hope i am doing it right! Thank you for the video!
I dont know how to do a Spectroscopy test. I hope that that wont interfere. Is it easy? Thanks
Thank you for the additional pictures. It seems there are two distinct types of crystal, twinned together. They could both be garnet, but maybe not. That could explain the specific gravity being slightly low. You should do the test again. It doesn’t hurt to have repeatable data.
The matrix material on the stone will affect the SG value as well. If the material could be completely removed, before taking the SG would help. Can’t guarantee that it will improve the number, though.
Funny thing about doing science… the numbers tell their own story. Sometimes they agree with the published data, and sometimes not. It is up to us to understand what they are saying.
good morning all jarryed here
Hi there Jennifer this gem is a Demantoid garnet coexisting with topazolite its natural counterpart! as they generally are! Please don’t sand it any father as it will de value your perches as this is a specimen grade gem and the value is in the size and natural appearance of its long forming growth lines, and the beauty that tells you about the millions of years that it took to get to rear size, this darker brown layer is part and parcel of the topazolite formation, as Garnets are part of a select few mineral types that can “enter exchange” meaning that they can cross with in there own family types with many differ colour variations and sub classes / outcomes and are becoming more well known now days. Because of there amazing colours and rearaty in som cases such as with Damantoids. As 90% of green gems in nature are rather scares to find in general, when it comes to gem grade minerals this meaning that they are faceable gem. pleas do go and take a look at topazolite and Demantoid garnets on IGS best and warmest regards Jarryed.
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Wow! It was sold to me as a duel garnet. I did not know what that meant though. It does look green underneath with brown around it. I thought the brown was just a matrix. I guess it might had some trancelucent polisded brown spots on top to it. I thought it was just polished close to the green gemstone itself. Maybe that is why he polished it. Can i classify this as a solid Demantoid garnet underneath and topazolite lawyered on top of the gemstone? It is 81.6 grams. If you were to make something with it the inside green would be Demantoid garnet so that would be sold as pure Demantoid garnet right? The brown garnet would be sold as topazolite seperatly right? Since it is so big it is split up able? topazolite garnet is around the outer edges of this rock right? That would be what i thought was all brown matrix! Should i still be trying to do tests to find out the value of this garnet? Thank you for all your help. I read that the biggest known Demantoid garnet is about 51 grams or something like that. Would this exceed the biggest Demantoid garnet in that resperct? What would the value be making jewelry with it? Leaving it alone in its natural state? I know that the bigger the gemstone is sometimes it is worth more being a bigger gemstone. Like what if you had 10 carats. Thanks
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Sanding a nice specimen seems very counterintuitive to me and not wise!
Dear Jennifer,
First of all congrats with such a nice specimen and certainly if indeed you got a rare big sized twin.
I can understand you being eager to know what is inside. But please do bear in mind that, as mentioned earlier on: sanding is a very agressive approach in opening up a gift to see what is inside.
Taking it apart to get the components out is another one. Just because you might get some valuable cut stones out of it?
The true value of a rare specimen is determined by it as a whole, not by the parts.
Having said that:
- stop any action until you know what you got and what approach is best to clean it: you might regret later on not having done so
- write down every step you think that could be done
- read about how it could best be done and whether it should be done at all: why do and why not
- if it turns out to be a valuable specimen and if your eagerness to see what is inside is bigger than what the endresult might be: please consider selling it to someone who has a more intricate knowledge of it
I am telling you this because I have made several of those rookie mistakes myself in the past (who has not), i.e. polishing up specimens to ‘improve’ on them, only to discover later on that then those were nót considered being specimens anymore…
Best regards,
Erik
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