Stones I have cut

lucaswilliam said:

Tried to scratch those green stones with a piece of quartz I have and don't think it scratched them

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Interesting. Try it on different faces in different directions as well as hardness can vary a little with the direction. It's quite pronounced when cutting a sapphire and other things can show it to some degree as well.

Lefty said:

lucaswilliam said:

Tried to scratch those green stones with a piece of quartz I have and don't think it scratched them

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Interesting. Try it on different faces in different directions as well as hardness can vary a little with the direction. It's quite pronounced when cutting a sapphire and other things can show it to some degree as well.

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Tourmaline hardness does vary with direction, but usually not by much (kyanite is the main mineral that varies greatly with direction, Moh 4.5 to 6.5 in a single crystal). However tourmaline will not be less hard than quartz in any direction - in fact some can exceed 7.5 in their hardest direction (even nearly 8). One study of variation of a single tourmaline crystal hardness with direction gave 1060 to 1540 on the Knoop hardness scale (Vickers is a third scale, one I use mostly for sulphide minerals and metals). This diagram is useful for converting between scales:



Of course if you have full tourmaline crystals, they will commonly show striae on their outer surfaces (peridot will not)



Lefty, tourmaline vary a lot in colour:

Just by looking at the stones shape it self it seems it is not tourmaline to me

Does anybody know of any labaratorys that can do mineral test or something of the sort jcu has told me that they only do commercial scale testing

Quarts is definatly not scratching it hhhhmmmm is refractive index a good way to determine wat a stone is or does it vary aswell

lucaswilliam said:

Quarts is definatly not scratching it hhhhmmmm is refractive index a good way to determine wat a stone is or does it vary aswell

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If quartz definately can't scratch it then it seems unlikely to be peridot - as Goldrocks says, peridot is typically a little bit softer than quartz.

Refractive index is one of the methods gemologists use to assist in identifying stones, unfortunately I don't have a refractometer. Like pretty much all methods used by gemologists, it's used to rule things out rather than make a definitive ID.

Do you have any photos of the stones without light behind them, so the features of the surface can be seen?

Also I have used a refractometer to test these stones but was didn't no I had to do it to a polished stone so it was the wrong reading I was told u need to polish a flat surface at 50 thousand diamond grit to get an accurate reading , so on Saturday when I go to the local lap club I will try it

Some of those almost have the look of sapphires (and some don't). Not some kind of garnet variety? Man this one is a stumper

lucaswilliam said:

Quarts is definatly not scratching it hhhhmmmm is refractive index a good way to determine wat a stone is or does it vary aswell

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Sometimes. but probably not in this case.

lucaswilliam said:

Does anybody know of any labaratorys that can do mineral test or something of the sort jcu has told me that they only do commercial scale testing

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Labs have to make a living (it is actually difficult to do so in this field). You need a geo friend to actually handle it and give a more intelligent guess - might only cost a beer or two

lucaswilliam said:

Just by looking at the stones shape it self it seems it is not tourmaline to me

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Does seem unlikely. Even when very waterworn and rounded, tourmaline will usually show some rod-like shapes.
That is a strong conchoidal to sub-conchoidal fracture - not a lot of minerals have it so strong. Try looking up fracture in some mineral tables (like the book I recommended), followed by sorting possibilities by colour (it may suggest something else - I am a bit busy at present).

Flame tests are worth a try, as they can give an idea of the main element the mineral consists of.

Just a quick glance at the shape of the smaller stones in the background reminds me of sapphires a bit. I've not handled a lot of tourmaline but none of the pieces that I have really look much like any of those.

Top photo, small stone in the top right hand corner of the pic - a passing glance would have me saying "that looks like a sapphire".

Maybe Lucas has had the good fortune to stumble across something not yet recorded in Australia? Whether it's worth anything or not, that would be a blast!

Tourmaline has a very recognisable crystal structure, totally unlike these stones. Have to agree with Lefty, these are looking very sapphireish

Dihusky said:

Tourmaline has a very recognisable crystal structure, totally unlike these stones. Have to agree with Lefty, these are looking very sapphireish

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Yeah, some of them really have that look dont they?

Lucas - whichever direction they show green through witn backlighting, try turning them through the opposite direction and pumping the strongest light you can through them and see if you can detect a really dark blue shade.

Lucas - the small, angular-looking stone in the top right-hand corner of your first photo.....it has the look of a roughly-formed sapphire crystal. If it's a typical blue-on-green sapphire, it will show green through the long side. See if you can get some really intense light to go down the "bum end" of that one and come out as blue at the pointed end or vice-versa.

My honest assesment is that if these are sapphires then they are probably a bit dark to be gem quality - but I wouldn't let that stop me from getting back out there and looking for more! We say on the CQ gemfield "where there is a bomb (non-gem quality sapphire), there is probably a good-un there somewhere".

If they are sapphires then the geo has mis-read the hardness - but that might not be difficult to do since hardness can be directional and sapphire shows this property of being noticably a bit harder in certain directions and a little less hard in others.

Sapphires have been found in your area I believe - you might have just found some more.

Those stones look very similar to ones i found lucas


Actually found them in a river that i was hoping to find sapphires but only found these. I checked and they are either yellow or green with light. I actually thought they were black until i read this post. Quartz did not leave any visible marks on my pieces

Manpa said:

I hope this is the appropriate spot for this, I bought a Brazilian Amethyst from Lefty which he cut for me. I've had it mounted by a manufacturing jeweller as a gift for the wife, no special Occassion, just to say I Love You and I'm glad the worst of her troubles are behind her.
As you can see it's simply stunning, the picture does not do it justice. Thank you Lefty.
https://www.prospectingaustralia.com/forum/img/member-images/11747/1537322757_image.jpg

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FP, here is the stone lefty cut