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Specific Gravity of Gold


garimpo

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Hey Don........

Sorry but I seem to be coming down with CRS, but years ago I used to use a mathmatical formula, which I can't remember..

Hopefully it rings a bell for someone out there.....anyway, after you zeroed out the scale with the container on it, you weighed

the specie dry, then added the water, weigh again, and then divide, or multiply the difference by a certain number, and

voila, your gold content.........from what I remember, quite accurate...........

maybe a science search of some sort......hav'nt got a clue where to find it.....sorry...........................~wyld~

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Need a lot of input here....I have this digital scale equipment for measuring how much gold is in

a "specimen" (quartz with gold)....anybody know if this is accurate or even close?....

It might not work because any formula that includes the weight of the water just measures the displaced amount of water to figure volume of speciman. But it would be easy to check using the normal formula and compare.

Gold mixed with quartz formula= 3.1 X speciman weight in water minus 1.9 X speciman weight in air

Set your scale on a 1x4 board suspended high enough to put a bucket of water under. Get a stick long enough to go across your scale with a inch on both sides and tie fishing line to each end that you can tie to your speciman or rock. Now put your stick and fishing line on the scale and zero it. Now weigh the nugget keeping stick on also = DRY WEIGHT. Now take your stick off the scale and tie the nugget to the stick so it will hang under the board and the scale. Put the stick back on the scale with rock hanging submerged in the bucket below= Wet Weight

I hope this makes sense and can help.

Randy

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Garimpo...

Your setup is nicely done but will give you incorrect results. The problem I see with it is the steel (or other metal) rack you are using will also have its weight effected by the water immersion and at a greater rate than a gold speci on it. That will distort your results by quite a bit IMHO. Most use thread to hang the speci from for that very reason.

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Need a lot of input here....I have this digital scale equipment for measuring how much gold is in

a "specimen" (quartz with gold)....anybody know if this is accurate or even close?....

Posted before post was finished...........

Jim

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If the entire setup is tarred with a known amount of water, then the speci placed into that same amount of water it should be accurate. Most would not do so and simply tare the scale, place the speci on the rack and add water then weigh again. That will give false results IMHO.

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Need a lot of input here....I have this digital scale equipment for measuring how much gold is in

a "specimen" (quartz with gold)....anybody know if this is accurate or even close?....

Don,

That is one elaborate piece of equipment, I have always wondered if the weight of the displaced water method was as accurate as the suspension formula. Almost everything I have heard or read on the subject, leads me to believe that both methods are off by as much as 10%. I think that to get some real comparative results, one would have to run the tests and then dolly the specimen and extract the gold. Another factor to consider would be how much other mineral may be present. I personally do not see where the metal platform would have any affect on the amount of displaced water if it is submerged by itself and that displaced water was disposed of before doing the actual test with the specimen on the platform.

Sure hope that you try both methods and let us know the results. Be sure and use distilled water since tap water has many impurities and salt water would be a no-no. Just my un-educated opinion.

Here is a link that describes both methods...........

http://www.rockpow.com/fieldtest.htm#Field

Jim

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You guys are great with the comments and help....Ok here's what I've been trying to do....

the scale for the larger specimen is a 2500 gram scale....for the smaller ones I use a 500 gr. scale..

the water and container is not being weighed...it sits on a support that straddles the scale without

touching it....I get the entire setup ready...that includes having water in the tank...then I tare the

scale to "0"....then I remove the basket and put the specimen in it and then lower it back into the

the water...the basket is then resting on the part of the frame that is being weighed so I should get

a "wet" weight.....for a dry weight I just weigh it normally....

My first weighin using the above method gave me these results: dry=1162gr, wet=926gr....

then I did away with the basket and tried the same procedure with a string and suspended the

specimen with a dowel across the weighing frame and got a "wet" weight of 929gr...an increase

of 3gr....and using Randy's formula I came up with 639.5 gr of gold in the specimen...but I also

believe that lotsaluck may be right in the fact that the metal basket takes up much more space

then just a string does....

I also did a smaller piece that had a dry weight of 7.5gr and wet was 4.7gr...using the formula

I came up with 0.2gr of gold...then I dollied (hammered) the gold out and it weighed 0.7gr instead

of the 0.2....

Anyway here's a pic of the specimen...1162 grams....

post-300-1217122486_thumb.jpg

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not so simple as it may appear

setup may be OK, resolution dependent on the scale used

repeatability may be dependent on air void content

the more severe problems lie with the assumptions regarding the sg of the native gold and the actual host rock

- if both can be appraised separately and the specimen vacuum impregnated with water, the results could be at least defensible

Bill

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Hi Garimpo and All

Why would you weight the water ?? Your doing this bas ackwards and all you need is the scale, dental floss, a small 1x4 and a metal coat hanger. If you weight the water and say it's 5 pounds and you add a one pound rock you have a total of 6 pounds if you tare the water out and add one pound rock you still have one pound wet rock DUH !! Garimpo take your scale and put it on a 1x4 set on books or buckets balanced and suspended over a pan or bucket of water Set the coat hanger hook down around the scale and 1x4 and flat top of the hanger on the top platform of the scale. Use a small piece of dental floss with a couple of slip nots wrapping the nugget and hooking it on the hook of the coat hanger. Adjust the water level to completely submerge the speci. Do not submerse any of the hanger hook only a minimum amout of floss. When your done thake the weight of the hanger and floss from the submerged weight and you will have an acurate weight of it suspended in water. Then throw that other stuff out. Save the water tub because you can use it in this process. Happy Huntin John B.

post-1056-1217140079_thumb.jpg

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Hi Garimpo

Something I forgot to add is thoughouly wash the rock with a dish soap and soak it for a brief time to let it soak water and release air for any fractures or cavities the soap will help break the surface tension on any bubbles that form and hopefully releasing them from the rock . Air bubbles or air pockets contained can through off the wieghts giving you incorrect weights adding boyance to the rock. Happy Huntin John B.

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Last post Garimpo

WTF is that ?? I'm trying to figure out this contraption ???? Whatever you do don't listen to lotsa luck or anybody whom thinks your setup will work ?? For they don't know sh98 about what your trying to do. A specific gravity test. You will need your dry weight and a weight of the item SUSPENDED in water. Not the weight of the water, water displacement or any other hair brained thing. This is not a hard process don't try and make it hard !! Happy Huntin John B.

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OK Gents,

Here is a direct Quote from "Fieid Guide of Rocks and Minerals".....

Specific Gravity: This means the weight of a substance in relation to the weight of the same "volume" of water.

Hope that helps to make your 'boat float'. :innocent0009:

Gary

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:coffeetime:

Or this quote........

Specific Gravity Definition

According to the "Dictionary of Geological Terms" the definition of specific gravity is as follows. "The ratio of the weight of a given volume of a substance to the weight of an equal volume of water." More accurately, "Specific Gravity is the ratio of the weight of a substance and the weight of an equal volume of pure water at 4 degrees C."

:innocent0009:

Jim

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BTW Nice specimen!!! I have noticed that most large pieces of gold matrix specimens have several varying densities of matrix. The best I think that can be gotten is more of a ball park figure on the gold albeit much more accurate than standard dry weight alone. If you measure the specific gravity of the matrix specific to the specimen and use it instead of just that of quartz it should be more accurate. Johnb ...if you look at the photos it is plain to see that water displacement is not being measured nor is it being weighed. Bob

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First of all folks thanks for all the "input"...I sure appreciate it...and I'm not trying to get this

specific gravity thing down to a perfect science....just a good ball park figure of how much gold is

in the specimen...

Second thing....the specimen is NOT MINE.. :wah2: ...I'm trying to help the poor b.....d that found

it and should sell for more money than he has ever seen in his life time....he's in his late 40's and

has never owned a house...this is his house payment....now that I think about it..I don't own a

house either.. :wah2: the four houses that I've owned in the past are now owned by ex-wives...

back to SG....the equipment that I use does not weigh the water and there is a difference in using

the basket vs string....I believe the string(floss) is more accurate....also does just weighing the nugget

by itself give a good "dry weight"?....I also like the idea of washing it in soap and water...did that long

time ago and soaking it to get out the air bubbles....

So far this is the weights that I have come up with: Dry=1162.2gr...Wet=929gr

Why all the fuss?...because someone in the USA wants to know so he can make an offer for it....

based on the amount of gold in the specimen.....

How many people ever find something like this in a lifetime?....it should be worth quite a few bucks

but how many?.....

BTW John B......since you sent pics and your "appratus" looks so simple I'm going to give

it a try also....

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Morning Steve....your right on about the HF treatment...that's what the guy in the USA is

thinking also...here in Brazil a person has to be licensed by the Gov. to handle acid...

I've already asked the one person here about that and he said he can get it but it's to dangerous

for him to mess with it....I agree because I have a 5 year old grand-son that it's impossible to

keep track of 24/7....

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First of all folks thanks for all the "input"...I sure appreciate it...and I'm not trying to get this

specific gravity thing down to a perfect science....just a good ball park figure of how much gold is

in the specimen...

Second thing....the specimen is NOT MINE.. :wah2: ...I'm trying to help the poor b.....d that found

it and should sell for more money than he has ever seen in his life time....he's in his late 40's and

has never owned a house...this is his house payment....now that I think about it..I don't own a

house either.. :wah2: the four houses that I've owned in the past are now owned by ex-wives...

back to SG....the equipment that I use does not weigh the water and there is a difference in using

the basket vs string....I believe the string(floss) is more accurate....also does just weighing the nugget

by itself give a good "dry weight"?....I also like the idea of washing it in soap and water...did that long

time ago and soaking it to get out the air bubbles....

So far this is the weights that I have come up with: Dry=1162.2gr...Wet=929gr

Why all the fuss?...because someone in the USA wants to know so he can make an offer for it....

based on the amount of gold in the specimen.....

How many people ever find something like this in a lifetime?....it should be worth quite a few bucks

but how many?.....

BTW John B......since you sent pics and your "appratus" looks so simple I'm going to give

it a try also....

Yes this is just an estimate and you won't know unless you break it up or refine it, however from what I have seen the gold content is usually higher than the formula shows. At $900 gold there is more than $18,000 of gold there.

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First of all folks thanks for all the "input"...I sure appreciate it...and I'm not trying to get this

specific gravity thing down to a perfect science....just a good ball park figure of how much gold is

in the specimen...

Second thing....the specimen is NOT MINE.. :wah2: ...I'm trying to help the poor b.....d that found

it and should sell for more money than he has ever seen in his life time....he's in his late 40's and

has never owned a house...this is his house payment....now that I think about it..I don't own a

house either.. :wah2: the four houses that I've owned in the past are now owned by ex-wives...

back to SG....the equipment that I use does not weigh the water and there is a difference in using

the basket vs string....I believe the string(floss) is more accurate....also does just weighing the nugget

by itself give a good "dry weight"?....I also like the idea of washing it in soap and water...did that long

time ago and soaking it to get out the air bubbles....

So far this is the weights that I have come up with: Dry=1162.2gr...Wet=929gr

Why all the fuss?...because someone in the USA wants to know so he can make an offer for it....

based on the amount of gold in the specimen.....

How many people ever find something like this in a lifetime?....it should be worth quite a few bucks

but how many?.....

BTW John B......since you sent pics and your "appratus" looks so simple I'm going to give

it a try also....

Don,

Not to complicate matters, but there are a number of ways to arrive at the same approximate answer with reference to your first inquiry. The displaced water can be weighed and a formula was provided in the first link that I gave you. I personally would not use that method as it is more complicated.

To gain a ball park figure, JB's illustration probably is as good as any method out there and it is a no brainer provided you use the proper formula. Knowing the approximate purity of the gold being tested would be a great advantage.

Here is another link that gives a couple LOOK-SEE illustrations and a whole bunch of pertinent information as well as a SPECIFIC GRAVITY ON LINE CALCULATOR to do your figuring for you.

http://home.att.net/~desert-gold-diggers/gold/specgrav.htm

If you know that you have pure gold in 100% quartz, then by all means use the JB method that is layed out in simple words in this link................ :unsure: :spinnin: :;):

http://www.gold-nuggets.org/specific-gravity-test.htm

Jim

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Randy and Jim...thanks for the input....I've never had the pleasure of dealing with something

this big but I would wonder if the value isn't more than just the gold value....

Each time I use one of the methods above I get a slightly different answer...possibly because

the matrix of the material surrounding the gold is many different minerals....gold found 100 yards

apart here can have a big difference in purity also.....

The owner is coming by tomorrow morning and since I've not had any firm offers I would guess

this beautiful specimen will be put under the hammer by noon....what a shame I'm not rich....

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The owner is coming by tomorrow morning and since I've not had any firm offers I would guess

this beautiful specimen will be put under the hammer by noon....what a shame I'm not rich....

Why not try to auction it on E-bay?

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