Fire Assay result explanation/ interpretation

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drtys

Member
Joined
Mar 5, 2020
Messages
21
Hello once again, I am hoping to get help in understanding the results from two ore/ rock samples that I recently had done?
Two Samples supplied. Both 31.0 grams each
Sample Preparation -
Pulverize up to 250 g 85% <75 um
Analytical Procedures
Au-AA23. Au 30g FA-AA finish
Instrument. AAS

Sample Description
Method. Au-AA23
Analyze. Au
Units. ppm
LOD. 0.005
~~~~
TAZ-20. 0.313
Target Range- Lower B. 0.279
Upper B. 0.325

Blank
Target Range- Lower B. <0.005
Upper B. 0.010

ORIGINAL 0.259
DUPLICATE. 0.220
Target Range- Lower B. 0.223
Upper B. 0.256
———————
ORIGINAL. 0.122
DUPLICATE. 0.133
Target Range - Lower B. 0.116
Upper B. 0.139
——————-

Sample Description

Method. WEI-21. Au-AA-23
Analyze Recess. Wt. Au
Units. kg. ppm
LOD. 0.02. 0.005

Sample #1. 0.03. 1.170
Sample #2. 0.03. 2.38
===============

Well that’s what I got so hopefully someone can help interpret this for an old timer?
Thanks All
 
LOD = Limits Of Detection. Their equipment will detect to .005 ppm (parts per million). Assays are reported in ppm. 1 ppm = 1gram per tonne ( 2200 Avardupois pounds). They usually will run a blank to see if the fluxes are in the proper proportion. After that, they run an original, then a duplicate (2 assays per sample) to see if even 1 small particle affected the numbers. In sample #1 I am pretty sure you have 1.17 grams per either kilogram, or per ton. #2, 2.38 grams per kg.,or per ton. This is where I would ask the assayer if they reported in grams per Kg., or grams per tonne. This has me confused also, on this report. Big difference in values.
I have not found a good size lab, that doesn't report in such a manner. Mainly due to increased use of the metric system here in the states. I miss the old reports that were issued in Troy ounces per ton (2000 pounds ). Made it a lot easier for us in the states.
 
Thank you both for your replies, I will be contacting the lab tomorrow to get the facts right.
 
Hey, talked to the lab where the assay was done and unfortunately I guess the end results were 1.070 ppm and 2.38 ppm per ton realized from two thirty ( 30 ) gram samples, so all in all not a very rich proposition if processing mostly by manual labour? Thanks all for the replies
 
drtys said:
Hey, talked to the lab where the assay was done and unfortunately I guess the end results were 1.070 ppm and 2.38 ppm per ton realized from two thirty ( 30 ) gram samples, so all in all not a very rich proposition if processing mostly by manual labour? Thanks all for the replies
Click to expand...
The ppm measurement do not need additional info.
It is parts per million and it is a relation number, as percent which is parts per hundred.
Your numbers is 1.070 parts per million parts or 2.38 parts per million parts
as 1.070 Kg per one million Kg or 1.070 pounds per one million pounds.

No need to complicate things :eek:
 
Sorry to hear of the low grades. I have had many disappointing results as well. On the bright side, you did the right thing by having an assay performed. Aren't you happy you didn't spend a fortune on buying a bunch of expensive equipment, that would more then likely cause you to end up losing more money? You have learned some very good knowledge though. One is that an assay, even though expensive, in the long run saved you a bunch of money. That is very smart. This is what all major mining companies do, because it works. If you find more propositions that you would like to test for, start acquiring the necessary tools for doing your own assaying. This is what I have done. Even though you will spend some money up front, it will eventually pay to do your own. The learning process of assaying is a very interesting process to learn. It will be more involved than basic refining, as you will have to learn some geology, more chemistry, constructing the assay lab, etc, but is valuable in the knowledge you will learn. And it is a really cool skill to learn, once you acquire them. On a side note, it probably will take about 100 assays to break even, once you acquire the necessary tools, equipment, and fluxes.
You didn't mention if it was a raw ore sample, or some concentrates.
Your result was comparable to many large quantity, low grade run of mine ore, processed in large open pit mines.
Don't discount selling to a major player, if you do not have a billion dollars of your own money to invest. The quantity of rock will determine if a large proposition is feasible.
 
Yggdrasil said:
The ppm measurement do not need additional info.
It is parts per million and it is a relation number, as percent which is parts per hundred.
Your numbers is 1.070 parts per million parts or 2.38 parts per million parts
as 1.070 Kg per one million Kg or 1.070 pounds per one million pounds.

No need to complicate things :eek:
Click to expand...
To answer your original question on feasibility to make money. That answer would be most likely a no. To mine, crush, grind, and recover the Au in a tonne of your material, would require the previous post conditions. On a small scale, you would have to do all that, for 1 - 2+ grams ($50- $100) a day, assuming you could do a tonne a day. Not worth it for me. I could make more $ flipping burgers at Mickey D's, for a lot less trouble and effort. Also, a fire assay will report for just about 100% of Au in the rock. Something very hard to attain in any milling or leaching plant. Recoveries can range from 0, to the high 90% range, depending on rock /Au relationships, and recovery method warranted.
 
goldshark said:
To answer your original question on feasibility to make money. That answer would be most likely a no. To mine, crush, grind, and recover the Au in a tonne of your material, would require the previous post conditions. On a small scale, you would have to do all that, for 1 - 2+ grams ($50- $100) a day, assuming you could do a tonne a day. Not worth it for me. I could make more $ flipping burgers at Mickey D's, for a lot less trouble and effort. Also, a fire assay will report for just about 100% of Au in the rock. Something very hard to attain in any milling or leaching plant. Recoveries can range from 0, to the high 90% range, depending on rock /Au relationships, and recovery method warranted.
Click to expand...
Why did you quote me in this?
 
Thank you gentlemen, the two samples submitted for assay. we’re just part of a five gallon pail of loose material collected from a large fissure/ crack in a large quartz boulder, located at bedrock level of a deserted gravel pit , which centuries ago was submerged river bottom, so actually for two ounces of material from a five gallon pail three quarters full it’s not to bad. Further exploration and sampling to be done once weather allows, and more reports to follow. Thanks much for all the info and advice/ help.
 
drtys said:
Thank you gentlemen, the two samples submitted for assay. we’re just part of a five gallon pail of loose material collected from a large fissure/ crack in a large quartz boulder, located at bedrock level of a deserted gravel pit , which centuries ago was submerged river bottom, so actually for two ounces of material from a five gallon pail three quarters full it’s not to bad. Further exploration and sampling to be done once weather allows, and more reports to follow. Thanks much for all the info and advice/ help.
Click to expand...
So it is placer Au then?
 
Weathered surface grabs always show poor results, now that you know there's gold in the vincitity take some core samples.
 
Last edited:
Hello maybe this can help to find gold in placer

the oldtimer do
Roasting black sand up to 700 C and put it hot with a Skimmer into a cold water bucket

it will crack the black sand and if it had gold inside will be exposed.

I do this few times with good result.
 
Testing placer, and testing hard rock ( in place ) are 2 different types of test. A pan used properly, will give a good test for recoverable placer gold. If you got 1 gram per tonne in a fire assay, that would warrant a full scale placer operation, almost, or at least another look by a qualified person. 1 gram means you are going to wash 30 tonnes of material to get 1 Troy ounce, or roughly, it is $60 per tonne material. That is very good, for a placer. The problem with fire assaying a placer operation, is that some or maybe even all the Au, was entrapped in the host rock. Or you could have even picked up a piece of float, which would not be truly representative of the whole of the material.
Since you haven't stated the exact conditions under which the sampling was done, perhaps a qualified geologist should have a look at it. Many gravel pits were mined strictly for gravel, mainly for roads or construction purposes, and the thought of checking for Au was the furthest thing from their minds. They also may, or may not, have known that the surface had very little, but the bottom could be very rich. Do some research to determine if it is patented ground, or open for staking, under the mining laws for that state. Do this before bringing in any body else. CYA.
 

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