Hydrogrossular Garnet vs Idocrase(Vesuvianite)

In West Sumatra in the regencies of Dharmasraya and
Solok Selatan there is a massive deposit of a usually
green colour stone(from yellowish to green) that I always
believed to be Idocrase;there are also finds in the rivers as boulders
as well as in the mountains
I tested in different laboratoriums and I got different results
2 labs say is Idocrase
2 labs say is hydrogrossular garnet
So I am really confused of what could it be
Maybe both minerals in the same rock?
If you make a search with google just search by
Batu Sungai Dareh(this the local name of this stone)
so you can see some pictures
Could it be Tsavorite?
Some pictures I uploaded to Flickr
[m.flickr.com]
Best regards
Alex

Hola Alex,

Your question is not easy to answer, can see there is not many posts in this thread. Analytical results are perplexing. Although its crystal structure is similar, idocrase and grossular should be distinguishable in XRD analysis.

Without knowing the area, my impression points to idocrase, don't ask me why.

Once resolved this issue, we could take care to identify the red mineral that appears in some of your photos...

Greetings

Josele

Vesuvianite and (hydro)grossular are both formed in skarns and can occur together.

Gracias José
Thanks Erik
Yes It's difficult here to find a gem lab in jakarta
who uses x-ray difraction
I should test better in a geology faculty lab maybe
in institute geology Bandung better than in a
gemologist
Best regards and thanks for replies
Alex Escobar Mercadal

One of the labs give me one reason why it's
not vesuvianite but hydrogrossular garnet and
this reason was that it has never been found
Crystals but allways massive and vesuvianite
allways found cristals in other localities in the
world
But as I read in some book in California the
Vesuvianite(Californite) never been found crystals
also but massive
Could be Idocrase also found as boulders in the
rivers?because in dharmasraya both places
is found this stone with very similar characteristics
being the one from river more translucent and
of some yellowish green colour
The area where are found is in Dharmarsya and
Solok Selatan in the highlands of Sumatra
Sane area there are iron mining,manganese mining
,gold mining,also found lot of garnet...
Mother stone of this mineral are skarns
Through these highlands cross the great Sumatran
fault and there are a few volcanoes,but the volcanoes
are some 4 or 5 hours away by car from location
of this stone
The boulders found in river batangharis that
starts in dharmasraya highlands and runs down
all through Jambi to meet the sea at malacca strait
Jose,the red stones that appear together with
some Idocrase? are jasper(I think)
This stone(Idocrase,hydrogrossular garnet or
whatever it is) is found most in green colour there
but also all the range from strong green to yellow
,pink and white
Just do a search by the name 'batu sungai Dareh'
in google or Idocrase sungai Dareh to see images
of it
They called locally Sumatran Jade but until
labs told Idocrase (but a few hydrogrossular garnet)
Best regards

Idocrase is what it looks like to me...some is probably the grossular and diopside is probably in all the stones....each particular stone is likely a mix..but idocrase is what is most likely prominent. For example, "Californite" is idocrase +/- "hydro-"grossular garnet....but they also have hydro-grossular ...but it is white, not green.

If you post some high quality pics on this Facebook site, we have a guy who has been testing (xrd) these stones and can give you a better answer than I can...may even test some for you.

[www.facebook.com]

~Zeke,
JadeJunkee
Washington State