Here's more about my job, did three places yet and there are many more coming.
1st week: that is the Preparation room 1.
At the beginning of the day, samples of ore are delivered in that room. Each is in an individual plastic bag of ~5-15kg with its number of sample. Samples maybe be big chunks of 1 dm of diameter and/or small gravel mixed with sand and dust of ore. They can be muck or not, anyway, they are all put in baking pans in the oven at 110°C to remove humidity and water if muddy.
Once it's dry, we start to crush samples in this machine to reduce the size, then we take a certain weight of sample, so we must select the good bowls (5%, 10%, 15%, etc). Then we make powder with the ore by spraying it with heavy rings that will crush the small gravel with their weight and spinning in a machine. Those are steps to homogenize the samples, which is a very important step to get a representative result when analyzing.
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2nd week: Preparation room 2.
Pretty similar, but this one is mainly for bigger samples because it requires more sample when ore is less homogeneous. (You know, the goal of analyzing samples is to get concentration of elements in an area. We usually always want the mean, so we take samples in various places of the area. If we sample only one place, it might not be representative, unless you're lucky.) 1st steps are the same, the changing things are that after the crusher, there is a roll crusher like this: -> 8 -> . 2nd thing changed is the sprayer, since sample is bigger, bowls are bigger. In room 1, bowls were like 10kg but in room 2, they must be like 18kg, so this is why we use a suspended machine to move bowls
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3rd to 5th week: Wetlab.
This room is called like that because we make solutions there and the sinks are there. There are many kinds of samples entering there. Let's start with the sprayed ore samples. We weigh them in numbered tubes. (It is very important to avoid mixing sample names and/or numbers obviously.) We add controls (concentration already known, so we can know when analyzing if it's wrong or not) and blank (no sample, just the matrix in what other samples are immersed. so if blank has a concentration of wanted element, it gonna be removed on samples). Then, we add nitric acid to turn sample in solution instead of solid, we add bromide to remove sulfurs (they turn to gas), we add chlorhydric acid to help dissolution and then we put tubes in a digester (it heats tubes to 110°C). We complete to make 50mL, shake, dilute then they are ready to analyze
Atomic absorption spectroscopy.
There are also gold/silver marbles (~2mm diameter). They come in glass test tubes and i attack them with nitric acid, then i put tubes in heated water bath (~95°C) for 10min. I make sure marbles are almost totally dissolved, I add chlorhydric acid and I put them again 10min in bath. Mix of those acids is called
Aqua regia and is very corrosive. A precipitate of silver is formed, which is wanted to analyze only the gold in solution. Once it's cooled down, we complete to 10mL, shake them and it's ready to analyze by Atomic absorption spectroscopy once again.
Incoming samples can also be liquid. If there's no gold, and metals are dissolved, we can simply shake sample then, put into test tube and it's ready to analyze. Approximated concentration of gold will determinate the method to use:
- >15g/ton: 10mL (or 5mL if solution's color is pretty dark) of sample is put in a powder mainly made of lead and silicon (let's call that Fondant, I'll explain what happens to this sample later in pyroanalysis)
- 0,2-15g/ton: 20mL with same technical
- <0,2g/ton: We put ~600mL of water (no need distilled water since sink's water doesn't contain gold), we add 50mL of chlorhydric acid and about 15mL of lead acetate. Now we put 200mL of liquid sample, we make a spike (any sample added with known gold quantity) and, like everywhere, a blank. Now we put beakers on hotplate with an aluminum rod to turn lead acetate (white) to lead (dark gray). Once no more acetate left, we remove liquid and make sure to avoid loosing the solid which is like a sponge. We make a ball with it with our fingers (ofc, we do wear gloves all the time). Then we put the ball in the Fondant
6th week to now: Pyro lab
The name says all: we put samples in furnace. But well, we do more that this. I past only one week in this section, so there are still many things i don't know or remember yet. In a first time, we put Fondant (couldn't find english word so here are links of definition:
1st and
2nd) in melting-pots and we weigh samples. Now it is the time to add extra stuff to play with the lead's weight. We add potassium nitrate (KNO3) or basic flour to (and I don't remember the following part) increase or decrease lead's weight. We stir the mixture and we cover with borax (sodium borate) samples with flour and we cover with soda (sodium carbonate). Once again, there are controls and blank.
Then we take sample board to bring in the furnace, which are ~1000°C. I wear the aluminum suit to avoid skin burns obviously and a tinted visor because light from furnace is pretty intense too. We enter four-by-four pots in the furnace with a capacity of about 24 pots, wait 50min then comes the HOT part: pouring melting-pots in diamond shaped molds. Lead goes in bottom because its heavier. (I'll try to get a picture of myself doing that) Seriously, I've never been so hot in my entire life! (and more, these days, it's so hot outside. Like 36°C everyday including humidity. So, just imagine in the furnace room, must be like 45°C and more...) It takes me like 15 long as hell minutes! And about 4min for used people... Well, I'll become faster with practice for sure. We wait a bit to let them cool down and now it's my favorite part: HAMMERTIME!
I hit the samples with a hammer to separate the lead in the bottom (containing silver and gold) and the glass over. Then with pliers, I hit the lead to make a badly shaped cube. Afterward, I put each lead cube in crucibles into the furnace. Lead is absorbed so only silver and gold left, a small marble is made, then it is hammered and gone to the Wetlab.
That's all for now, more coming when I'll try other sectors
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maybe next year 
