Gold in rocks I can see ?

[Bobby]

Hello experts .

Whats the formula for doing a gold content specific gravely test on a ironstone haematite / quartz specimen that shows rich gold visually ?

Wish I could show a pic but can't seem to do it on this site ? 

Bobby.

[Alluvium]

Hi Bobby,

How's things up at the Hill? I see plenty of rain forecast that way.

Here are a couple of ways to work it out.

Regards Alluvium.

PS;  I will try and send on a Specific Gravity Chart I have made up.

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Checking gold content in a specimen using digital scales.

Firstly weigh the dry specimen on the digital scales and record it.
The measurement we need to find now is its weight in water.

Use a styrene drinking cup or a very light container that is big enough to hold the speci, slowly add water so that it will be completely submerged by the water when it’s placed in the cup, but is not displacing any water at this time.                                                                  

Place the cup on the scales, and then tare them to Zero.                              

Tie a piece of cotton or light fishing line around the speci, so that it can be suspended in the water.

Dangle the speci, in the cup of water, make sure that it is not touching the bottom or sides of the container and is fully submerged, weigh and record.

 When you have the dry weight and the wet weight, it is easy using a formula for determining the gold content.                                                                                                                        

The formula now for determining the gold content in the quartz is:                                                

(Weight of rock in water x 3.1)                                    

minus                                                                                                        

(Weight of rock in air x 1.9).                                                                                                                  
=======================================================================

.
Example: -                      Dry weight  = 100 grams.
                                                
                                      Wet weight = 78 grams (suspended in water on scales).


                                Wet = 78 x 3.1 = 241.8 grams.    Dry = 100 x 1.9 = 190 grams.      


Subtract lesser from greater =         241.8 — 190 = 51.8 grams of gold in the specimen.

 If there are minerals in the speci that are heavier than quartz like ironstone etc, then the estimate will run high.

========================================================================      


SPECIFIC GRAVITY OF A QUARTZ & GOLD SPECIMEN.



THE  FORMULA.

                                    Dry   Weight in Air
                        ___________________________                  =      Specific Gravity  (SG.)
                                              
               Dry  Weight in Air   ---   Weight in Water  


EXAMPLE.

                  

                   4.5 Ozs.                                       4.5                        
 ________________________      =        ________          =       4.5   -:-   .5   =  9.00  ( SG.)

          4.5 Ozs    --    4. Ozs                             .5

 

9.00 on the specific gravity chart  =  82.39% ------   Now multiply the weight of the DRY specimen by the percentage of Gold.


   Example  --------------                     4.5 Oz     x    .8239    =     3.70 ozs .     of Gold in the specimen.


This formula is for a Quartz & Gold specimen; if the gold were in Ironstone a new table would have to be calculated.   The specific gravity of Ironstone varies from 4.9 to 5.3 depending on locality.
                    See attached :- Gold Chart List for Specific Gravity / Percentage details.                                                                          

                       ( SG.)                          SPECIFIC  GRAVITIES.                                          (SG.)
                    
Platinum         21.45                                                                                        Iron                  7.87
                                                                                                            
Gold               19.32                                                             Ironstone  ------  Magnetite         5.13            
                                                                                                                         Hematite          4.9 to 5.3
Palladium       12.00
                                                                                                                         Basalt              3.21 – 2.74
Lead               11.34
                                                                                                                         Serpentine       3.10 – 2.80
Silver              10.49
                                                                                                                         Diorite             2.99 – 2.72
Copper            8.96
                                                                                                                         Quartz Diorite  2.90 –2.62

Nickel              8.90                                                                                          QUARTZ        2.65
                                                                                                                          Water               1.0


                                                                                                            

                                                                                                                                                        

[Huego]

Hello experts .

Whats the formula for doing a gold content specific gravely test on a ironstone haematite / quartz specimen that shows rich gold visually ?

Wish I could show a pic but can't seem to do it on this site ?  

Bobby.

Bobby,

Posting pics of your specimen is not hard. When posting a topic look at the "additional options" (below the message you are typing). You can browse you computer for pics and select the one you wish to post. Only warning is make sure the pics size is not too big otherwise its a  pain to view. A pic is worth lots of words.

Cheers, Huego

PS: With highly mineralised quartz working out the "gold content" using SG is not possible with any accuracy because the SG of the matrix is unknown (because it's not pure quartz). There is a big difference in SG between quartz and the common (mixed) iron oxides gold is often found with.   You might need to crush/dolly and pan the crushings.  

[Bobby]

Thanks Alluvium ' for all the formulas , the rain we have been getting is more then anyone can remember , out bush the green vegetation is starting to make the place look like New Zealand !

Hi Huego ,
I've tried using the 'options' to post a pic but for some reason it won't work for me ?

The specimen has a mix of Ironstone , Hematite & quartz so it would be imposable to get a accurate gold content as you said , its  nice looking  so dolly potting it could be a mistake regarding its value , what do you think ?

Cheers
Bobby.

[Huego]

Bobby,

If its a nice looking specimen it may be best selling it to a collector, as a display piece (even I may be interested in buying form you!).

You could get an estimate of gold content by using the formula & quartz figure for SG followed by using the closest "ironstone" SG figure (haematite is a rusty red brown and magnetite if its blackish). The gold content will be somewhere between the two gold content figures you get. You may need to agree with the buyer on content. He may pay the upper figure, then again he may not.

If you sold it on Ebay you can say the gold content is between this figure and that & explain why. Gold content is always the best indication of value unless the specimen is extraordinary in some way (in beauty or crystalline etc).

Can't imagine what your problems posting pics may be. This is what I do. I size them, post them on the desktop or file, "browse" desktop see button on right of window, find & select them. Their id is then shown in the attachment window but they won't show in a preview. When you hit post they should show up with your message.

Hope this is helpful.

Cheers, Huego  

[Alluvium]

Hi Bobby,

Hopefully, here is the S/Gravity Chart.

You may have to right click on it and open it with Adobe Reader.

Regards Alluvium.

[Alluvium]

Hi Bobby

Your Quote;   The specimen has a mix of Ironstone , Hematite & quartz so it would be impossible to get a accurate gold content as you said.

The first table by volume, would be the best one to give you some idea of the gold content.
It will be a bit on the high side.

If you want a more accurate figure you have to work out an S/G, say for % of Ironstone + % of Quartz.

Taking the details on the S/G of both of these in table 2, you could come to some compromise using them with your guesstimates on the % of I & Q in the speci added together.

Or get a mathematician to work this out.

Regards  Alluvium.

[Bobby]

Thanks for the chart Alluvium , but now I feel like a dope   

Huego , appreciate the photo posting info , I'll try again when I have more time 

Cheers
Bobby.