Specific Gravity On Specimen

[geof_junk]

The bases of finding the wet weight is based on floating principle that water sg is 1gm/cm³ so suspending a specimen in water will add the volume in cm³ to the water weight to gm.  So a bowl of water weight will increase by the volume of the specimen as it is lowered in the bowl. From this if the weight increase is taken from the dry weight you have the wet weight.

Method of doing this is putting the bowl of water on a scale note the reading (or zero scale). The increase is in weight from suspended specimen is subtracted from the dry weight.

Most people do not relies that if the volume of gold in the quartz is 7 times smaller than the quartz volume then the weight of each is 50/50 so ½ of it is gold by weight.

[mn90403]

48 minutes ago, fourtyniner said:

Here's some better shots of the specimen.

You need a jeweler to assess the best options for that piece.  You might want to leave it as is and just put a clasp on it for a pendant or it could become a ring or ...

It has a lot of character now.  We bought a piece from Wes.  He has experience with jewelers.

[Bedrock Bob]

12 hours ago, GotAU? said:

Sounds like an interesting way to do it using a triple beam. I will have to experiment with this technique a bit more. Thanks!

Exactly the same as the illustration above. Only with the triple beam. There is a hook down under the pan for the wire to hang down through a hole in the table. They are made to facilitate a mass density test.

The problem is the wire (or string) and how you have it connected to the specimen. It's easy to get some wire down in the water and that throws off your numbers a little. If you use a horsehair and a tiny drop of CA glue and only submerge the specimen to the connection point things are pretty accurate. If you use copper wire and wrap it around the nugget things are off quite a bit. The devil is in the details of how you suspend the specimen and how much rigging gets below the surface of the water. 

Another thing to consider is the waste rock. If it's just quartz it's not a big problem. If the gold is in a chunk of cemented gravel or gossan it becomes a lot more complex. 

[GB_Amateur]

46 minutes ago, Bedrock Bob said:

The problem is the wire (or string) and how you have it connected to the specimen. It's easy to get some wire down in the water and that throws off your numbers a little. If you use a horsehair and a tiny drop of CA glue and only submerge the specimen to the connection point things are pretty accurate. If you use copper wire and wrap it around the nugget things are off quite a bit. The devil is in the details of how you suspend the specimen and how much rigging gets below the surface of the water.

The wire has volume and weight.  You can determine these (measure the weight, compute the volume knowing length of wire in the water, diameter of the wire, and its density) and adjust for them.  A bit tedious, but doable.

Another (also tedious) solution is to use monofilament sewing thread.  (This is similar to monofilament fishing line, but much, much smaller diameter ==> less volume.)  The weight and volume of that is so minimal it's lost in the measurement errors, meaning it's meaningless at affecting the final answer.  But the issue with this is difficulty in making it into a sling.  It's difficult to see and thus difficult to work with.

I've used both of these 'tricks' and can't really say which I prefer, although as I get older and my eyesight gets worse, the mono thread is sufficiently frustrating that I tend towards the former.

While we're exposing these devils in the details, there are a few other uncertainties in these methods which propagate to uncertainties in the final answer:

1) Are there other (compounds/minerals/contaminants) in the specimen besides quartz?

2) Are there any voids (hidden air pockets) in the matrix?

3) What is the purity of the gold alloy (which in the very least affects the density value used in the calculations)??

For most of the typical calculations discussed in this thread the assumptions are 'no', 'no', '100%' -- unrealistic.  Keep that in mind when you've arrived at your final answer.

 

 

[mn90403]

Get a fish scale and rig your nugget in a little mesh.  Weigh it dry and then submerge the nugget and get that weight.

This works for specimens of 3-4 ounces or greater.  Less than that no one cares!  haha

[Bedrock Bob]

36 minutes ago, GB_Amateur said:

The wire has volume and weight.  You can determine these (measure the weight, compute the volume knowing length of wire in the water, diameter of the wire, and its density) and adjust for them.  A bit tedious, but doable.

Another (also tedious) solution is to use monofilament sewing thread.  (This is similar to monofilament fishing line, but much, much smaller diameter ==> less volume.)  The weight and volume of that is so minimal it's lost in the measurement errors, meaning it's meaningless at affecting the final answer.  But the issue with this is difficulty in making it into a sling.  It's difficult to see and thus difficult to work with.

I've used both of these 'tricks' and can't really say which I prefer, although as I get older and my eyesight gets worse, the mono thread is sufficiently frustrating that I tend towards the former.

While we're exposing these devils in the details, there are a few other uncertainties in these methods which propagate to uncertainties in the final answer:

1) Are there other (compounds/minerals/contaminants) in the specimen besides quartz?

2) Are there any voids (hidden air pockets) in the matrix?

3) What is the purity of the gold alloy (which in the very least affects the density value used in the calculations)??

For most of the typical calculations discussed in this thread the assumptions are 'no', 'no', '100%' -- unrealistic.  Keep that in mind when you've arrived at your final answer.

 

 

That is exactly what I said in slightly different words.. Keep that in mind when you arrive at your final answer.

[Redz]

Tare the scale with your wire already suspended in the water

[Bedrock Bob]

7 minutes ago, Redz said:

Tare the scale with your wire already suspended in the water

That was the solution I came up with the first time I did it! (thanks Youtube!).

I tared the scale with a few inches of wire under the water. I put a mark on the wire at water level. Then I took it apart and tied up the specimen. Then got it all back underwater up to the mark.

It worked. It told me what I needed to know.

I have no idea how close my numbers were to the actual ratios. Close enough to make some basic assumptions on what I had.

 

[matt]

Wes has the correct method and diagram.

I always used dental floss to tie the specimen and suspend in water. I wrote an article in the ICMJ explaining both methods of specific gravity measurement and actually used a nice specimen to test both methods for accuracy. I used hf acid after the specific gravity testing to dissolve the quartz and have only the remaining gold. It was pretty accurate. I'll see if I can scan the article and post it here.