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#51

malri_au
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From: Adelaide & Victoria
Joined: 02 February 2018
Posts: 454
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06 February 2018 11:50 am

coal would be the carbon source in this instance then aye?


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#52

goldierocks
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Joined: 10 January 2015
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06 February 2018 02:56 pm

Yep, and the slag would be carbon derivatives wink


Robert Benchley...
I have kleptomania, but when it gets bad, I take something for it.

#53

22shells
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Joined: 11 September 2014
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11 February 2018 08:34 pm

Here's something different I found today, there's meant to be common opal in the area. Thinking that's what this might be? Or could be something else?
1518341681_p2111013.jpg

1 user likes this post: 7.62marksman

#54

pete165
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Joined: 24 October 2017
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11 February 2018 10:37 pm

Hi
It is called opalite . My Uncle had buckets of the stuff in his garage.

#55

22shells
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Joined: 11 September 2014
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11 February 2018 11:27 pm

Thanks pete, I'll have to look that up. Thought it looked a bit opally. First bit of it I've found, I'll go back and try and see if there's any more.

#56

goldierocks
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Joined: 10 January 2015
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12 February 2018 10:27 am

Yes, common opal for sure (opalite another term for it, of many)


Robert Benchley...
I have kleptomania, but when it gets bad, I take something for it.

#57

22shells
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Joined: 11 September 2014
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12 February 2018 09:11 pm

Cheers goldierocks thumbsup Here's some stones I found last year, I have no idea what they are, but they're from a different spot a long way from where the opal was. I just picked them up because they looked good, and I'd never seen them before in other areas. Would be good to know what to call them, not expecting them to be rare as there were quite a few there, but only in this one spot.
1518430255_p2121014.jpg

#58

goldierocks
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13 February 2018 09:51 am

It is tricky with such dark photos - also it is a good idea to quote their properties like hardness when asking (see separate section). Even experienced geos sometimes have problems when they are actually holding the specimens so remote identification like this requires all the additional info we can get (photos may ber essential, but they are often of very little use except in reducing hundreds of possibilities to a dozen or so). However they look like they have sub-conchoidal fracture and are very fine-grained, so they are probably essentially silica rocks of some type (eg microquartz = chalcedony), which scratching them to test hardness will tell you. Such as banded cherts etc.


Robert Benchley...
I have kleptomania, but when it gets bad, I take something for it.

#59

22shells
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Joined: 11 September 2014
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13 February 2018 04:34 pm

Thanks goldierocks, yeah that photo came up a bit dark so I took another one in the sunlight. I haven't done a hardness test yet but that would probably be the next step if photos don't work. I realize it's hard to tell just from a photo.
1518500081_p2131014.jpg

#60

22shells
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18 February 2018 08:08 pm

Here's an unusual crystal I found today. It's quite hard, and has six flat faces- almost like a cube. Pretty sure it's not quartz because quartz crystals normally have a hexagonal cross section with a point, and this has four sides with a flat top and bottom as well. The strange thing about it is that it seems to have fractures running in two different ways- both vertically and horizontally. Tried to get a couple of pics:
1518944917_p2181016.jpg

#61

22shells
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Joined: 11 September 2014
Posts: 163
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18 February 2018 08:11 pm

Tried to get a pic of the crack lines going in two different directions:
1518945053_p2181015.jpg

#62

22shells
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Joined: 11 September 2014
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19 February 2018 07:31 am

Did a bit of research on it last night. Although I thought it was hard, it actually scratched easily with a small screwdriver. I'm thinking it's probably calcite? When I found it I was hoping it was topaz, but I don't think it is now.

#63

Chiron52
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From: Wollongong, NSW
Joined: 26 May 2017
Posts: 434
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20 February 2018 12:04 pm

I would say calcite.


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#64

Keen Ken
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Joined: 19 February 2013
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20 February 2018 04:06 pm

Hi, 22shells, I think calcite is a bit more rhomboidal shaped, like the second picture.
Looks to be a monoclinic crystal form, if it is very easy to scratch with the screwdriver it could be gypsm (hardness 2).
Calcite is trigonal, hardness 3. calcite effervesces with diluted(10%) HLC acid or sulphuric acid, ( Try CLR).

#65

Rockhunter62
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From: Townsville, QLD
Joined: 03 May 2016
Posts: 1,307
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20 February 2018 06:43 pm

Maybe moonstone.

Cheers

Doug


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#66

22shells
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Joined: 11 September 2014
Posts: 163
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20 February 2018 08:18 pm

Cheers thumbsup This photo from above it looks a bit rhomboidal shaped:
1519118299_p2201017.jpg

#67

Keen Ken
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20 February 2018 09:05 pm

Yes, I agree, but the hardness is 6.5. would need to be a very hard file to scratch it .
Thought the sheen on the previous picture was camera flash, Orthoclase Feldspar
Again hardness will be the key.

#68

Heatho
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From: Sydney, NSW
Joined: 29 April 2013
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21 February 2018 07:49 am

Looks like calcite to me.


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#69

goldierocks
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Joined: 10 January 2015
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22 February 2018 09:30 am

22shells wrote:

Thanks goldierocks, yeah that photo came up a bit dark so I took another one in the sunlight. I haven't done a hardness test yet but that would probably be the next step if photos don't work. I realize it's hard to tell just from a photo.
https://www.prospectingaustralia.com.au … 131014.jpg

All you need is a $2 coin, a pocket kinife blade and a bit of quartz to test most hardness. I suspect these would be harder than the coin and probably harder than the steel - almost certainly some sort of chalcedonic silica.


Robert Benchley...
I have kleptomania, but when it gets bad, I take something for it.

#70

goldierocks
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Joined: 10 January 2015
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22 February 2018 09:33 am

Chiron52 wrote:

I would say calcite.

You said hard - calcite is soft (hardness 3) so can be scratched by a $2 coin and easily with a pocket knife point. I agree it looks like it is a different crystal system. but keep oin mind that both crystal faces and cleavage planes for planar surfaces. Need hardness....


Robert Benchley...
I have kleptomania, but when it gets bad, I take something for it.

#71

goldierocks
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Joined: 10 January 2015
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22 February 2018 09:44 am

Keen Ken wrote:

Yes, I agree, but the hardness is 6.5. would need to be a very hard file to scratch it .
Thought the sheen on the previous picture was camera flash, Orthoclase Feldspar
Again hardness will be the key.

Hardness 6.5 rules out a lot of suggestions. Are you sure it is scratched by quartz and it does not scratch quartz. Feldspars like orthoclase are really so clear because they have twinning and exsolutions - usually white, cream or even red or green (and only translucent in thin slivers). This is quite transparent. It is almost certainly not quartz. If it were harder than quartz I might have suggested topaz, although the cleavage angles look incorrect.....


Robert Benchley...
I have kleptomania, but when it gets bad, I take something for it.

#72

22shells
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Joined: 11 September 2014
Posts: 163
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22 February 2018 01:55 pm

goldierocks wrote:
22shells wrote:

Thanks goldierocks, yeah that photo came up a bit dark so I took another one in the sunlight. I haven't done a hardness test yet but that would probably be the next step if photos don't work. I realize it's hard to tell just from a photo.
https://www.prospectingaustralia.com.au … 131014.jpg

All you need is a $2 coin, a pocket kinife blade and a bit of quartz to test most hardness. I suspect these would be harder than the coin and probably harder than the steel - almost certainly some sort of chalcedonic silica.

Did some hardness tests:
The chalcedonic type rocks- must be fairly hard, not scratched by $2 coin (left coin traces on rock), not scratched by pocket knife, not scratched by sharp quartz crystal fragment (wore away a bit of the quartz)
The "calcite" type crystal- seems soft, not scratched by $2 coin (coin isn't real sharp), scratched easily by pocket knife, scratched easily by sharp quartz crystal fragment. Guess that rules out topaz? Only other thing it might be that I can think of could be aquamarine, but I doubt it. Likely area for aquamarine and it has been found in the area, but the shape of it doesn't look right for aqua to me.

#73

goldierocks
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Joined: 10 January 2015
Posts: 795
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22 February 2018 03:24 pm

22shells wrote:
goldierocks wrote:
22shells wrote:

Thanks goldierocks, yeah that photo came up a bit dark so I took another one in the sunlight. I haven't done a hardness test yet but that would probably be the next step if photos don't work. I realize it's hard to tell just from a photo.
https://www.prospectingaustralia.com.au … 131014.jpg

All you need is a $2 coin, a pocket kinife blade and a bit of quartz to test most hardness. I suspect these would be harder than the coin and probably harder than the steel - almost certainly some sort of chalcedonic silica.

Did some hardness tests:
The chalcedonic type rocks- must be fairly hard, not scratched by $2 coin (left coin traces on rock), not scratched by pocket knife, not scratched by sharp quartz crystal fragment (wore away a bit of the quartz)
The "calcite" type crystal- seems soft, not scratched by $2 coin (coin isn't real sharp), scratched easily by pocket knife, scratched easily by sharp quartz crystal fragment. Guess that rules out topaz? Only other thing it might be that I can think of could be aquamarine, but I doubt it. Likely area for aquamarine and it has been found in the area, but the shape of it doesn't look right for aqua to me.

Beryl (aquamarine) is harder than quartz, Coin doesn't have to be sharp. if softer it will leave a smear of metal on the sample. Chalcedony is much the same hardness as quartz - its correct mineralogical name is microquartz (so just very fine-grained quartz) - not the same as opal which is a different mineral.
Fluorite (sometimes clear) seems unlikely (can be clear but not rhombohedral shape) - apatite colour wrong and rarely shows cleavage. Things like dolomite and mmagnesite are harder than calcite (especially magnesite) but I rarely see those carbonates as transparent crystals (but can occur):

https://www.google.com.au/search?q=magn … DjHeoNbmUM:

Magnesite can be as hard as 4.5 - so a possibility. It reacts with hot dilute hydrochloric acid (but neglibly with cold acid, unlike calcite and to a lesser extent dolomite). If you powder some finely and drop powder into a candle flame. the flame should go bright white.

https://geology.com/store/collections/

Last edited by goldierocks (22 February 2018 03:26 pm)


Robert Benchley...
I have kleptomania, but when it gets bad, I take something for it.

1 user likes this post: malri_au

#74

Keen Ken
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Joined: 19 February 2013
Posts: 202
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23 February 2018 10:24 pm

There is a transparent lightish yellow orthoclase feldspar (called Labradorite) found near Casino NSW, It looks similar in crystal structure but yellow.
The hardness is a puzzler though, "scratched easily by pocket knife" though I have managed to scratch quartz with a pen knife using extreme force, (more like a crushing fracture)a knife blade is about 5.5 to 6 from memory so leaning more towards Feldspar on that one.
Looking at an enlarged picture the internal parallel structure could be lamella twinning that occurs in the Labradorite from Casino. The top face on the first picture of the crystal does not look like cleaved face as there is a cubed piece sitting on one end that would be unlikely to be left if the piece had been cleaved, also note there is a conchoidal fracture internally in the top of the crystal that runs about 1/2 way down behind the front face and 1/2 way across the right front which would have cut across the apparent cleavage plain.

The white rocks with the dark areas look a bit like Chert or quartzite. There is a type of opalised wood that has similar colours but has a definite wood structure, Those piece are not that)
All Quartz minerals are 7 on the Mohs hardness scale, this includes Chalcedony, Agate, Quartz crystal, massive Quartz, Amethyst, Citrine, Jasper (impure form) even petrified wood that is formed from silica enrichment.

Topaz is 8
All beryls including Emerald, Morganite, Heliodor, Aquamarine, are all 7.5 to 8 on the Mohs.

Corundums are 9 Mohs scale (Ruby, Sapphire)
Diamond of course is top the list at 10

Everybody who fossicks should get themselves good hand Loupe and a copy of a good geology text book as an aid to Identifying there finds. Gemmology and Mineralogy seem to be streets apart when it comes to text books so it's probably good to have one for each.
Physical properties are the biggest clue (lustre, appearance, crystal form, hardness, cleavage etc.), then the diagnostics through Refractive index, Specific gravity, Xray fluorescence. etc
It's all part of the fun.

I love collecting the concentrates from a gold pan, drying them out and examining them under a 20x to 40X Gemological stereo microscope.
It's amazing the different type of crystal I find, even found a minute diamond crystal from some old Stanthorpe tin concentrates.
Most interesting was 3mm long green apatite crystals form another location, if only they were 3 cm :-/

Having studied Gemmology I still have a 3rd copy of Goubylins? GEMS, a fantastic reference book with outstanding photographs for it's time.
Also I have a copy of Sinnkankas? Mineralogy that I found indispensable and still pull out from time to time.
The instruments I payed big money for (and had to save to get) are now available on eBay for a fraction of the cost.
A simply hand loupe is you best tool, you may even see identifying inclusion. Now that's a whole new world! totally amazing.

Hope this helps.

1 user likes this post: malri_au

#75

22shells
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Joined: 11 September 2014
Posts: 163
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26 February 2018 10:24 pm

Cheers guys thumbsup Ken- after I run a sluice, then run the cons through the clean up sluice, then take those cons and pan them out for gold, when I get right to the end of panning I often get these tiny little red stones amongst the gold and black sand. I call them garnets, not sure if they are though but they must be heavy. Too small to test for hardness. I do have one of those small hand loupes, use it all the time.
1519644205_p2261018.jpg


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