SG test results 3.444444 , so do we call it spinal ? my book quotes black spinal at 3.5 - 5.1sg and doesn't quote obsidian .
Identify my rocks of interest.
- Thread starter aussiefarmer
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Tourmaline / spinel mabey
Conduct the streak test from here or scratch
Conduct the streak test from here or scratch
It scratches the back of a tile , cut it really didn't wear any of rock
No color in the streak?
no streak to me its a good old tile are they all porcelain
I recon Sphene. S.g = 3.5
Can you scratch it with a knife ( somewhere ugly, on the rock
)
Can you scratch it with a knife ( somewhere ugly, on the rock
)
do it need to scratch the brown layer off the tile and try again , it seems to cut into the white layer pretty easy
I would say no it seems to have left silver of knife on rock
could it be corundum ?, I have been getting sapphires there , its in my creek, I am more interested in finding gold but plenty of other gems of interest keep popping up. I have got gold but its inconclusive until I get back down there as I didn't bang my matt out before I started and I think it may have come from another site I was exploring.
geosam
Sam
Even though I initially thought it was a black sapphire I do agree with Atomrat here about the possibility of it being spinel. I have seen many sapphires with Depends where you found it. If it's around New england then yeah i suppose it could be as there are a few obsidian outcrops around that area. Obsidian is extremely brittle as well i've got some at home with me now and just a hit with a geological hammer could smash it to a few smaller flakes. If you got any quartz try scratching your piece on some quartz. Just do a few hardness tests and try to narrow down what it could be.
geosam
Sam
Sapphire and ruby are just names given to different variants of corundum but since you have been getting sapphires in that region then I would say its probably a sapphire or a spinel (found with sapphires) it definitely looks like one. Give it a scratch with some quartz and see if its harder
all righty I have redone the SG , as my scales only go one decimal point in grams, but they do however weigh GN( grains 0.0648 of a gram) so I did the maths and now we have a more accurate SG of 3.769. I wouldn't have thought the extra decimal point could blow the figures out like that , I better buy some scales that go atleast 4 decimal points hey.
original maths grams
3.1 divided by 0.8 = 3.4444444444
new maths
49 grains 13 grains times 0.0648
grams
3.1752 divided by 0.8424 = 3.769230769
original maths grams
3.1 divided by 0.8 = 3.4444444444
new maths
49 grains 13 grains times 0.0648
grams
3.1752 divided by 0.8424 = 3.769230769
geosam said:
thanks mate
its harder than quarts, the quarts leaves a streak on it then I wiped the quarts off and there's no mark on it
Now we have it's SG and streak colour I would say it's Pleonaste (Black Spinel), it's SG is close enough if you factor in a slight error due to not being done in a lab. Totally different SG to Obsidian and pretty much spot on for Spinel.
Nice sized piece too.
Nice sized piece too.
aussiefarmer said:geosam said:
thanks mate
I hate doing hardness tests, very subjective and inconclusive mostly if you only have smallish bits to work with..... Just my opinion though.
I must say I appreciate this its giving me hands on experience of the tests I have read .
its giving me hands on experience of the tests I have read .geosam
Sam
Heatho - Yeah you're not wrong there mate, I just use it as a way of narrowing down what it could possibly be you can't rely on hardness test for definitive results
aussiefarmer - glad we could be of help mate
aussiefarmer - glad we could be of help mate
So the jurys saying black spinel ? (heatho with a like from atomrat)
can I ask why its not corundum ?
if its spinel can it be cut and polished into a nice stone ?
I have a lot of smaller pieces also, is it worth saving ?
I also thought one other bit was until I shined light through it and it had a lovely deep green color so I guess its sapphire ? I will have to light test the rest now 8)
can I ask why its not corundum ?
if its spinel can it be cut and polished into a nice stone ?
I have a lot of smaller pieces also, is it worth saving ?
I also thought one other bit was until I shined light through it and it had a lovely deep green color so I guess its sapphire ? I will have to light test the rest now 8)
You should have mentioned the 'smaller pieces' earlier hahahaha. Yes it certainly can be faceted and turns out great
Currundum is closer to 4 with s.g I'm pretty sure
And yep the green one would most likely be sapphire too sometimes corundum can have a barrel or 6 sides shape
Currundum is closer to 4 with s.g I'm pretty sure
And yep the green one would most likely be sapphire too
sometimes corundum can have a barrel or 6 sides shape
AtomRat said:
My apologies' :8 back in august when I started the thread I only had that one rock , especially with the glassy break , that's what intrigued me.
I hand picked that one when I was prospecting trying to find a starting spot to pan . but since then I have run the sluice and collected a few and a few sapphire's.
All in all I have seen enough signals to say its worth continuing and hopefully I can hit some gold
