⭐ Gemstone & Mineral Show n Tell

[LONEWOLF]

Glass used in bottles has a lower hardness than Obsidian (volcanic glass).... Under a loupe you can see the fracture planes and can tell the Difference... There are variances in this method, but a good 'Guide' to tell the difference... The older the bottle the more difficult it is for this method to work as there are many types of glass used in bottles over the years...

LW....

 

[user 4386]

"Obsidian . has a hardness of roughly 5 - 5.5...... On Mohs scale of hardness, obsidian is about 5, which can just be scratched with glass".

Most glass is hardness 6-7 (up to 9 for gorilla glass, not used for bottles). Its silica content, which commonly is the main determining factor for its hardness, varies from 50% to 90%.

So it is in the eye of the beholder - the problem being that the composition of obsidian varies as much as the composition of glass - it commonly varies from 65 to 80% silica. Your observation might well work using the same piece of glass in a single volcanic province - but you are better than me if you can easily detect 0.5 difference in hardness anyway...

I find it bloody difficult in any new area - once I know an area, things like colour are usually more useful, also flow layering and tiny included crystals in obsidian. I doubt that I am ever 100% confident without such features (of course the way it occurs geologically is a clue - if it is not just an isolated fragment)..

 

[LONEWOLF]

So true goldierocks, My understanding was that bottle glass had a hardness of around 3... Think I need a better hardness table... :Y:

When it comes to Identification there are many things that can vary... Generally it's my eyes that vary tho.. :lol:

LW....

 

[Colmaca]

Shiny rocks is good

 

[Gilly47]

shiny rocks is good alright

ray

 

[Dappa]

Hi guys found these last weekend in reedy creek in the sluice topaz maybe and a sapphire

Also found this today up in murmungee range found some good rock samples hopefully got some yellow stuff as well

 

[Lefty]

Interesting little yellow crystals there.

Yes, top one looks like either topaz or quartz.

 

[Wally69]

Got a last minute opportunity to hitch the van up and turn left out of the driveway. Made our way north to where the lightening is rumoured to hit the ironstone ridge and found a little bit of colour with the family :rainbow: arty: :rainbow:

 

[Billy]

Nice one Wally!!

I like the "ridge" on the top of that pretty rock.

Great time of year to be anywhere under the Aussie cross :Y:

 

[Heatho]

Geez mate, that's a decent trip. Pity Shauno is out prospecting for gold at the moment, he likely would have been more than keen to catch up and show you around.

Nice stone.

 

[Lefty]

Looks like a nice find there Wally :Y:

Can't really tell from the photo - is it worth doing anything with? I can see what look like some nice flashes of colour.

 

[RockRat]

Found a few of these yesterday, not clear ,more yellow in color,
others iv'e found were clear.color change in the clay, a gemologist
friend said they were ..Jack Straw Crystals. Anyone one heard
of that term. thanks in advance.

 

[Heatho]

Never heard of that name before but I love rutilated or tourmalinated quartz, very nice.

 

[user 4386]

Never heard of that name before but I love rutilated or tourmalinated quartz, very nice.

Jackstraw refers to the shape of the inclusions, not the mineral - they can be all sorts of things (tourmaline, rutile, epidote). Interesting specimen.

 

[RockRat]

thanks for that, so what are the shapes goldilocks,,
the difference i can see with others i find is that
the tourmaline is scattered in the crystal, others
have the tourmaline coming from the bottom.

 

[RockRat]

A few more .

 

[user 4386]

thanks for that, so what are the shapes goldilocks,,
the difference i can see with others i find is that
the tourmaline is scattered in the crystal, others
have the tourmaline coming from the bottom.

Jackstraws? Like long thin tubes or straws or hairs. The position simply depends on when the tourmaline started or stopped growing relative to the quartz. The silicon that forms quartz is unlikely to become depleted in the solution from which the quartz is growing, compared with things like sodium, iron, boron and aluminium which are required in addition to silicon to form tourmaline. It could conceivably also be a temperature effect due to cooling of the fluid (quartz will tend to crystallize down to low temperatures, probably tourmaline will not). Since the fluid will be water, the oxygen and hydrogen required for these minerals will always be present.

Nice specimens!

 

[Lefty]

Neat specimens thereRockrat! :Y:

 

[RockRat]

A cluster coming out a couple of weeks ago,
soak the ground so don't break. like the mud

 

[J Treasure]

Freshly dug saph and zircon. CQ gemfields