Please help me identify this stone, is it possibly green quartz?

[Sarahandkez]

Please ignore my lack of knowledge lol this is a new world to me but I found this big boy today in the Gloucester area, I’m not 100% because it’s so rough and dirty. Going to polish the bottom first when we get home so I can update you all then it’s hard to capture the colour in photos but it looks more green in person and was definitely sparkling a little in the sun. Any help is appreciated

 

[Jaros]

Dunno mate.

 

[Pro-oz]

Don't know, bought a stone once was told it was green quartz? but it's clear with a green tinge to it, this bit was about the size of my fist have been slicing bits of it to facet, cuts and polishes has a better sparkle than topaz I reckon.

 

[grubstake]

It's not quartz, that's for sure - quartz isn't a granular rock, which this is. There may be some thin quartz veinlets amongst the the black grains and greenish stuff, but I'm not sure whether the white bits I can see are real or just an effect of the lighting.

 

[LONEWOLF]

+1 for not quartz... Not the best pic to give you an answer..

LW...

 

[Nightjar]

Chalcopyrite or mudstone?

 

[AKA_RedRimmed_Desert]

Looks similar to a glaucophane we have here, came down from Canada during an ice age. Don't know if you can still get black sand paper (as they sold years ago) but medium fine sanding paper when black ice age glaucophane will sand off a bluish white dust. It is a type of sodium amphibole. Other similar looking materials give a yellowish or tan chalky dust.

 

[Hawkear]

Good post to spend a bit of time on going through my Rocks and Minerals book. Without the benefit of hands on my best guess is maybe a fine grained Peridotite (Kimberlite). Peridotite is the main rock of the earths mantle and when exposed on the Earths surface it is usually coarse grained due to the eons of gradual cooling and weathering needed for its exposure which allows for the growth of larger crystals.
Occasionally when it is erupted much faster in a volcanic event, Peridotite assumes a much finer grained appearance due to more rapid cooling and is then referred to as Kimberlite.
Kimberlites are the source of most of the diamond deposits of the world.
The attached image shows a Kimberlite rock with some mineral and diamond enclosures.
I believe Diamonds have been found in the New England region of NSW before.
Maybe crack open a fresh face and look for any enclosed minerals.
Good Luck.

 

[user 5263]

Could be Serpentine

 

[Sarahandkez]

Thank you so much for all your suggestions, I’m gonna give him a good clean sand and polish, I’ll post an update

 

[Sarahandkez]

Don't know, bought a stone once was told it was green quartz? but it's clear with a green tinge to it, this bit was about the size of my fist have been slicing bits of it to facet, cuts and polishes has a better sparkle than topaz I reckon.

Oooh good to know, I’m gonna cut a big slice so fingers crossed we get a sparkle lol

 

[Sarahandkez]

Good post to spend a bit of time on going through my Rocks and Minerals book. Without the benefit of hands on my best guess is maybe a fine grained Peridotite (Kimberlite). Peridotite is the main rock of the earths mantle and when exposed on the Earths surface it is usually coarse grained due to the eons of gradual cooling and weathering needed for its exposure which allows for the growth of larger crystals.
Occasionally when it is erupted much faster in a volcanic event, Peridotite assumes a much finer grained appearance due to more rapid cooling and is then referred to as Kimberlite.
Kimberlites are the source of most of the diamond deposits of the world.
The attached image shows a Kimberlite rock with some mineral and diamond enclosures.
I believe Diamonds have been found in the New England region of NSW before.
Maybe crack open a fresh face and look for any enclosed minerals.
Good Luck.
View attachment 304

This was super helpful thank you! It looks like a very similar texture to this too! We got a smaller piece that seems to have more quartz veins and is a lot more sparkly so this makes sense, will post an update tonight

 

[LONEWOLF]

Could be Serpentine

That was my Guess as well, but really need a closer pic...

LW...

 

[Hawkear]

My interest was tweaked because I have seen rocks like this before and had been racking my brain to remember but have just remembered now. It was in Gippsland on the Tanjil river when I was dredging for gold in the days before it was banned.
The area I was in was called Blue Rock, now the site of the Blue Rock dam. The rocks stood out in the river bed out from the other rocks with their pale greenish blue look. I also remember reading a report on the goldfield by an early geologist for the Victorian geological survey who suggested the "blue" rocks were igneous dyke material (probably now identified as peridotite or Kimberlite) associated with the ancient Volcanics in the area.
It never occurred to me to examine my fines for diamonds or other precious stones.
Does the Sydney museum offer an identification service? Also look at geological maps for the area and they provide a clue.
PS regarding the veining, dykes in situ over time can suffer cracking and infusion with quartz and other mineral charged fluids resulting in quartz veining. They can even be highly auriferous and the best known is the Morning Star Dyke at Woods Point where the miners just followed the dyke downwards encountering quartz vein after quartz vein which carried very rich gold.

 

[Nick34]

Could be as simple as it looks and that's Greenstone

 

[Hawkear]

Greenstone is a more generic term and can also include jades and other rocks of greenish hue and has no specific lithologic definition.
The Archean greenstone belts of the WA cratons are widespread and associated with the mantle layers that were close to the surface in those Archean times.
In other places the only way they mantle rocks could be brought to the surface was from deep eruptions through overlying rocks and are therefore less widespread and much younger but still of the same mantle layer composition. Because these eruptive events occurred quickly they brought diamonds to the surface at such speed that they were prevented from oxidising (burning) before the dyke cooled.
If you've ever wanted to see a diamond burning just you tube or google it. Diamonds are common in mantle rocks but rare at the surface for this reason.
Diamonds are a result therefore of the eruptive speed and rate at which the dyke rock cooled.
For all of that we are probably talking about the same rock Greenstone, Peridotite or Kimberlite.

 

[AKA_RedRimmed_Desert]

Lamproite ore form of peridotite, from diamond pipes can form a crystalline shape similar to a raw diamond. I dug this specimen at Arkansas Crater of Diamonds park.

 

[user 5263]

You said that you found it in the Gloucester area, I was wondering whereabouts in the Gloucester area. I have a booklet somewhere about the Barrington Tops area minerals and gemstones which may be of some help.

 

[Pat Hogen]

Looks like a copper-based oxide or sulphide.

 

[user 4386]

My interest was tweaked because I have seen rocks like this before and had been racking my brain to remember but have just remembered now. It was in Gippsland on the Tanjil river when I was dredging for gold in the days before it was banned.
The area I was in was called Blue Rock, now the site of the Blue Rock dam. The rocks stood out in the river bed out from the other rocks with their pale greenish blue look. I also remember reading a report on the goldfield by an early geologist for the Victorian geological survey who suggested the "blue" rocks were igneous dyke material (probably now identified as peridotite or Kimberlite) associated with the ancient Volcanics in the area.
It never occurred to me to examine my fines for diamonds or other precious stones.
Does the Sydney museum offer an identification service? Also look at geological maps for the area and they provide a clue.
PS regarding the veining, dykes in situ over time can suffer cracking and infusion with quartz and other mineral charged fluids resulting in quartz veining. They can even be highly auriferous and the best known is the Morning Star Dyke at Woods Point where the miners just followed the dyke downwards encountering quartz vein after quartz vein which carried very rich gold.

Not kimberlite and probably not peridotite - more probably a mafic diorite. I studied the mineralogy of these Tanjil rocks 54 years ago. The same as at Woods Point. They also contain gold-bearing quartz veins at Tanjil.