In 1977 I worked in a gold mill. Knob Hill mining Republic Wa. This is how we process the ore to recover 99% of the gold. After the crusher and clarifier the very fine ore was put into some solution that included pine oil. The pine oil frothed up making foam. On top of the foam you could see lots of trails of gold. Really they often were "gold bubbles". Paddles with air bladders would rotate, horizontally, through the foam, slopping it over the outside edge of the container. This "concentrate" would fall to the floor of a locked room below. Thsi would go straight to the smelter. When I first saw in the room the concentrate had been shaped into a long row wall to wall about a foot wide at the top and about 6-8 inches deep. The sides we sharply slopped so an accurate measurement could be taken. The next step is where I took over. The muddy solution that was left over (about the density of a thin milk shake) was sent to two large cylindrical containers. Chemicals were added here and then the solution was sent to many other vats of similar sizes until it ended up at the thicker. The "thicker" is the same as they use in a sewage treatment plant. 60' foot across and 3 stories high. The gold was suspended and reduced to a particular size using cyanide. This (clear as drinking water) "Preg" (for "pregnant" with gold) would spill over the side at the top. It would then be combined with zinc in some vacuum chamber. After this the only thing left was gold, silver, zinc particles that combined at a very exact size. This was ran through four locked tanks that held "sock" like bags. (we called it the bag tanks) 144 socks in each of the four tanks. When removed the each held about 10-12 inches of this gold rich concentrate. The water was then pumped back up to the mine. I always thought the process was facinating.
Hi Jason, Excellent experiment! You've probably got at least 100 You-Tubers that would love to be your "lab" assistant! Your down-to-earth explanations make you a pleasure to watch and learn from!! You're a GREAT teacher! Thank You for all your hard work & research! Stay Safe! Jim
Have you tried a similar test with litharge instead of lead? If the gold particles are very small (likely in sulfides) they will have trouble settling through the slag to the lead. We have a problem with vaporization from the resin, up to 50% losses if we ash first. However with a litharge fire assay we get good agreement with the solution mass balance and XRF of the resin. Freezing up for the season tomorrow, so we will move from the mine and mill to the lab for the winter.
I am a geologist at a underground gold mine with a similar hydrothermal low sulfidation qtz vein and agree 100%, while you are seeing free milling gold in the samples theres likely tons more gold bonded with sulfides and possibly telluride complexes as well. Would love to see a video of litharge vs pure lead. Love the vids as always, thank you Jason!!
I'm going to brainstorm. The insulation on the furnace is lacking. The flame needs a short run to burn then contact the crucible. The incoming air needs to blow upwards, surrounding the burner to keep it from melting. Use enough air to combust the gas, any excess will cool the crucible. A stainless sheet around the crucible will reflect heat in. Insulate the outside. A thick piece of cast for the lid. A chimney to outside. Carbon monoxide is poisonous. So are metal fumes etc. Just some ideas for a permanent furnace. Love watching. Great show!
Another factor driving the choice of chemical is your desired environment within the crucible. If you want a reducing atmosphere with the crucible, then you would certainly use the carbonate. The CO2 will be heavier than atmospheric oxygen and act as a barrier to intrusion into your melt. If you desired an oxygenating environment, then the carbonate would be counter productive.
@@EngGuy63 Metalogical meaning : metals being examined in a logical procedure. My latest word creation. Can be used in metallurgy or chemistry or physical properties. You have my permission to use it appropriately.
I really appreciate your doing these experiments. They answered some questions I had. Please continue with the experiments, as I find them very educational. Thanks.
Good experiment - and a good outcome - confirms that it doesn't matter what the starting compounds are it's the flux composition that matters. I wish more people understood how to set up experiments. Pick a hypothesis and try and _disprove_ it. Fail early and fail often. Eliminating things that DON'T work is much faster than trying to get it right first time.
For a while, in industry, the off gasses from roasting sulphide ores was the principal source of sulphur dioxide that was then oxidised on a platinum catalyst to make sulphuric acid, without which the motor car just wouldn't start.
Really good work Jason. I too was hoping for a richer sample, however I have some low grade stuff that I may recover in a similar way. Glad it seems like there’s little difference in the recipe results. Terrific, enjoyed, thanks sir ✌️PT
Jason, I saw a test report of flux ratio between na2co3 and naoh long time ago. Flux wise, 5% naoh + 95% na2co3 combination is the best recovery in the report. (Raw material is deselnized anodic slime)
I would suggest redoing it on a bigger scale. If they are the same then you might as well use the one that requires less to get the job done. only problem is without a known quantity of precious metal you don't know what your recovery rate is.
As always enjoyed the video thank you if I ever hit the motherload I'm going to hire you to melt my gold and teach me and I'll give you 50% as always I enjoyed thank you for the video and teaching me how to do this I appreciate it can't wait for the next one
This the only way I reach out to others. Choose some one else. I’m in for the pure enjoyment.watching others do what they do best. Thank you any way. Mike
With so much lead used per smelt vs recovered goal metals, could you use the lead button as a collector for many smells, without pupelling it each time?
I know it’s a lot of work and not really worth it but would you ever do a gold/silver button separation? As well as showing how to get the silver back from the nitric acid? Thank you so much for all the videos I have learned so much!
Frothing and bumping play merry hell with any reaction, whatever the temperature . At much lower temps where standard glassware is used , it will at least contaminate distillations , and even destroy your glassware . Testament to just how much energy is in play even in everyday things like a boiling pan of water or a vehicles coolant system . Also , the CO2 makes the reaction more acidic , at least until it all off gasses . You should see little difference in recovery efficiency with most sulfide ores between the CaCo3 and the CaOH .
While the recovery is reasonably close I have to ask 2 questions. 1) which costs more to get? If the sodium hydroxide winds up costing more you aren't really saving anything even using less of it, the amount is not that big a difference for your use. 2) if the costs are comparable so the sodium hydroxide is costing about the same, which outgas would you prefer? The co2 which is a hothouse gas or the water vapour which has a cooling effect? Yes the actual amounts are small so it isn't really a big concern for MBMM but the answers might change some viewers plans.
I agree with you 200% I think 20 muleteam borax has it's place. And it boils like mad. I Wrote Jason this . Jason, I have been told that sodium makes for silver losses. It destroys platinum too. The only recipe for platinum I can find is 10 to 1 borax. Now I ask you, how much silver is lost? any gold lost? The oxidizer? burning up stuff. Where is the flour or charcoal. Where is the reducing atmosphere? You use an OXIDOZER. I think if you look into the boiling point/burning point of sodium is near the temps you use. I have heard of guys using lower temps/longer times? and getting better returns. You can't have metal AND burn it. A traditional Turkish goldsmith would take a round clay coffee cup looking thing and layer silver powder and then screened charcoal. Multiple layers and then covered with a lid of damp clay.. Now that's a reducing atmosphere. You need to look up David Hudson, Oremus on you tube. Mono atonic gold has an S5 orbital or something that makes it act like a halogen (Sodium and chlorine are halogens/) You couldn't forge anything out of that. It burns up. My guys use resin to dissolve the gold. But burn up the gold getting it out. Same deal on the arsenic / acid then put into charcoal. How to get it out of the charcoal without burning it up. I have a prospector playlist that has it if you can't find David Hudson. Yellow metal of gold is AU2. AU is white or black or green and possibly clear , depending on how it is annealed. It's a rabbit hole bud. Thanks for your great videos
I do believe in REFINING. dunking the lead back in. But with all the sodium and heat.....you can triple your losses. What if you didn't dunk it in. Use 30g lead each time. Try a borax control smelt and compare?
I don't think there is a "best" flux or method. I think it all depends on the chemistry of the ore and as that changes so will the flux. There's likely a very good middle ground/average but I doubt there is a one size fits all recipe.
Hi Jason, I have some sulfides that I want to smelt. They’re mostly made up of Galena, Pyrite and minor amounts of Chalcopyrite. How did you determine how many moles of sodium hydroxide to use based on your cons?
Hi Jason , I just referred you to Minor 49er , looking at a mine he has been into recently, looking at the walls color looked really good I mentioned to him to take samples, I'm sure he needs help with that kind of stuff .. I instantly thought of you... hope he takes my advice and contacts you... R/Steve
I don't go to sites that say Text me at another place. I think it's a scam. Pioneer Pauley had the same problem with that... So sorry look for another sucker.
Hi Jason, the only way to do an accurate test is to have samples with known quantities in them. Then you can measure after the test and see how much has been recovered. Does it help to pour the molten metal/flux quicker in to the test mold? For some reason it seems to me that more flux flowing with the metal rather than less flux would recover more metal. How porous does the crucible get? It looks rough making it tougher to pour from.
The recipe for Platinum smelt is 10 to one borax. No sodium. It burns platinum I am seriously squinting at the sodium I am using.. How much burned up the exhaust? I heard it may hurt the silver too. Gold? Who knows? i think it has to do with the boiling point of sodium.sodiom bicarbonate boils a 2912 F
Asking just out of curiosity, not a criticism, but isn't this chemistry well-known after hundreds of years of recovering gold from ore? Or have large operations all done something different (like cyanide leaching) so this isn't as well understood as it could be? Enjoy the videos!
Wondering if you can reclaim the lead from the used cupel? I reclaim lead oxide (dross) back to pure pb using carbon (sawdust) to remove the O atoms releasing Co2 in my bullet casting operations
Interesting to see some original ore. I have a vein of sulfides that is easy to get to and assays 0.08/ton on the relatively clean sulfides. Have always wondered if that one is able to be made into some profit.
@@paulcoover9197 1 percent of a ton is 20 lbs but the grade reported is 8/100s of an ounce per ton or about three grams. With buyers margin you could figure 120 per ton which might be great if a huge volume and a big company could be intrested. But for a small miner diging a ton a day 120 if perfect recovery minus costs is just about wages
sodium burns up Platinum. How about silver and gold? you need a reducing atmosphere Keep the oxygen out. old timers used grease and wheat flour or charcoal.
In 1977 I worked in a gold mill. Knob Hill mining Republic Wa. This is how we process the ore to recover 99% of the gold. After the crusher and clarifier the very fine ore was put into some solution that included pine oil. The pine oil frothed up making foam. On top of the foam you could see lots of trails of gold. Really they often were "gold bubbles". Paddles with air bladders would rotate, horizontally, through the foam, slopping it over the outside edge of the container. This "concentrate" would fall to the floor of a locked room below. Thsi would go straight to the smelter. When I first saw in the room the concentrate had been shaped into a long row wall to wall about a foot wide at the top and about 6-8 inches deep. The sides we sharply slopped so an accurate measurement could be taken. The next step is where I took over. The muddy solution that was left over (about the density of a thin milk shake) was sent to two large cylindrical containers. Chemicals were added here and then the solution was sent to many other vats of similar sizes until it ended up at the thicker. The "thicker" is the same as they use in a sewage treatment plant. 60' foot across and 3 stories high. The gold was suspended and reduced to a particular size using cyanide. This (clear as drinking water) "Preg" (for "pregnant" with gold) would spill over the side at the top. It would then be combined with zinc in some vacuum chamber. After this the only thing left was gold, silver, zinc particles that combined at a very exact size. This was ran through four locked tanks that held "sock" like bags. (we called it the bag tanks) 144 socks in each of the four tanks. When removed the each held about 10-12 inches of this gold rich concentrate. The water was then pumped back up to the mine. I always thought the process was facinating.
Hi Jason, Excellent experiment! You've probably got at least 100 You-Tubers that would love to be your "lab" assistant! Your down-to-earth explanations make you a pleasure to watch and learn from!! You're a GREAT teacher! Thank You for all your hard work & research! Stay Safe! Jim
Agree 100% 👍
Have you tried a similar test with litharge instead of lead? If the gold particles are very small (likely in sulfides) they will have trouble settling through the slag to the lead. We have a problem with vaporization from the resin, up to 50% losses if we ash first. However with a litharge fire assay we get good agreement with the solution mass balance and XRF of the resin. Freezing up for the season tomorrow, so we will move from the mine and mill to the lab for the winter.
I am a geologist at a underground gold mine with a similar hydrothermal low sulfidation qtz vein and agree 100%, while you are seeing free milling gold in the samples theres likely tons more gold bonded with sulfides and possibly telluride complexes as well. Would love to see a video of litharge vs pure lead.
Love the vids as always, thank you Jason!!
The greatest contribution anyone can make to their field is to try new things and see what delivers better results.
I'm going to brainstorm. The insulation on the furnace is lacking. The flame needs a short run to burn then contact the crucible. The incoming air needs to blow upwards, surrounding the burner to keep it from melting. Use enough air to combust the gas, any excess will cool the crucible. A stainless sheet around the crucible will reflect heat in. Insulate the outside. A thick piece of cast for the lid. A chimney to outside. Carbon monoxide is poisonous. So are metal fumes etc. Just some ideas for a permanent furnace.
Love watching. Great show!
Man i love going to school with you. You explain and teach us so much.
Thanks!
Another factor driving the choice of chemical is your desired environment within the crucible. If you want a reducing atmosphere with the crucible, then you would certainly use the carbonate. The CO2 will be heavier than atmospheric oxygen and act as a barrier to intrusion into your melt. If you desired an oxygenating environment, then the carbonate would be counter productive.
As a retired Industrial Chemist I enjoy the metalogical chemistry.
@@EngGuy63 Metalogical meaning : metals being examined in a logical procedure. My latest word creation. Can be used in metallurgy or chemistry or physical properties. You have my permission to use it appropriately.
I’d rather use my own made up word metalytics. metal-analytics 😅
Meta logical really, if you don't think about it.
Enjoying the smelting videos, thanks Jason for sharing.
Just commenting in support of a great channel. Keep up the good work Jason.
I love this series. Please feel free to get geeky with the chemistry and maths.
I really appreciate your doing these experiments. They answered some questions I had. Please continue with the experiments, as I find them very educational. Thanks.
Good experiment - and a good outcome - confirms that it doesn't matter what the starting compounds are it's the flux composition that matters.
I wish more people understood how to set up experiments. Pick a hypothesis and try and _disprove_ it. Fail early and fail often. Eliminating things that DON'T work is much faster than trying to get it right first time.
🔥 I've always wondered,,,,how much GAS is burnt during these test ????🔥
That cost is part of the process too.
Thanks brother
Always worth a look. I'm just happy to learn something new every time 🧐
Thanks man 👍 I love this stuff so much I built a big stainless steel furnace. I still need some big crucibles . Keep the content coming !
Your shaker table and hammer mill are pretty good Jason.
I love the energy you put into your explanations……..for me it’s “geological gold”……..keep them coming…….I love your channel!!
Thanks Jason, always enjoy your videos!
Great comparison test. Good luck! 👍
For a while, in industry, the off gasses from roasting sulphide ores was the principal source of sulphur dioxide that was then oxidised on a platinum catalyst to make sulphuric acid, without which the motor car just wouldn't start.
Since the lead weighs less after the first firing, is it lost to the atmosphere or is it in the slag? Love these videos!
Really good work Jason. I too was hoping for a richer sample, however I have some low grade stuff that I may recover in a similar way. Glad it seems like there’s little difference in the recipe results.
Terrific, enjoyed, thanks sir
✌️PT
Very good video Jason. I like how you break it all down. Good job! Like you I was hoping a better yield. Thanks for sharing!
Use soapstone in your molds to make it release easier. Sticks are really cheap and it works great.
Jason, I saw a test report of flux ratio between na2co3 and naoh long time ago. Flux wise, 5% naoh + 95% na2co3 combination is the best recovery in the report. (Raw material is deselnized anodic slime)
Thank you, Jason. I love your experiments!
I would suggest redoing it on a bigger scale. If they are the same then you might as well use the one that requires less to get the job done. only problem is without a known quantity of precious metal you don't know what your recovery rate is.
I was really surprised that neither one did significantly better. I guess like you said you'll need to do more tests.
Good video, and your chemistry is impressive, was never my strong point.
As always enjoyed the video thank you if I ever hit the motherload I'm going to hire you to melt my gold and teach me and I'll give you 50% as always I enjoyed thank you for the video and teaching me how to do this I appreciate it can't wait for the next one
Very interesting and informative video you are doing so well keep up the amazing work five stars brother
Keep up the science. It's a service to everyone I the field.
A chemist I was not. However it is fun watching you.😊
This the only way I reach out to others. Choose some one else. I’m in for the pure enjoyment.watching others do what they do best. Thank you any way. Mike
Love the comparison great video Jason
Very interesting experiment ! Thanks !!!
I have some old anhydrous soda ash here but all the SodiumCarbonate I can buy here (EU) these days is in a deca hydrate crystal form.
cool experiments Jason :)
With so much lead used per smelt vs recovered goal metals, could you use the lead button as a collector for many smells, without pupelling it each time?
I've wondered that as well. Would it just get more and more concentrated with precious metals?
@@SMOBY44 Yep, it totally can.
I know it’s a lot of work and not really worth it but would you ever do a gold/silver button separation? As well as showing how to get the silver back from the nitric acid? Thank you so much for all the videos I have learned so much!
Check out sreetips here on YT he does refinement and separation using the exact method you're talking about.
I second watching Sreetips.
Frothing and bumping play merry hell with any reaction, whatever the temperature .
At much lower temps where standard glassware is used , it will at least contaminate distillations , and even destroy your glassware .
Testament to just how much energy is in play even in everyday things like a boiling pan of water or a vehicles coolant system .
Also , the CO2 makes the reaction more acidic , at least until it all off gasses .
You should see little difference in recovery efficiency with most sulfide ores between the CaCo3 and the CaOH .
While the recovery is reasonably close I have to ask 2 questions.
1) which costs more to get? If the sodium hydroxide winds up costing more you aren't really saving anything even using less of it, the amount is not that big a difference for your use.
2) if the costs are comparable so the sodium hydroxide is costing about the same, which outgas would you prefer? The co2 which is a hothouse gas or the water vapour which has a cooling effect?
Yes the actual amounts are small so it isn't really a big concern for MBMM but the answers might change some viewers plans.
Thank you Jason dying to see this
Great methodology and video. Thanks.
The frothier sodum carbonate may enhance the convection currents in the melt, bringing the precious metals into contact with the collector metal more.
I agree with you 200% I think 20 muleteam borax has it's place. And it boils like mad. I Wrote Jason this .
Jason, I have been told that sodium makes for silver losses. It destroys platinum too. The only recipe for platinum I can find is 10 to 1 borax. Now I ask you, how much silver is lost? any gold lost? The oxidizer? burning up stuff. Where is the flour or charcoal. Where is the reducing atmosphere? You use an OXIDOZER.
I think if you look into the boiling point/burning point of sodium is near the temps you use.
I have heard of guys using lower temps/longer times? and getting better returns. You can't have metal AND burn it. A traditional Turkish goldsmith would take a round clay coffee cup looking thing and layer silver powder and then screened charcoal. Multiple layers and then covered with a lid of damp clay.. Now that's a reducing atmosphere. You need to look up David Hudson, Oremus on you tube. Mono atonic gold has an S5 orbital or something that makes it act like a halogen (Sodium and chlorine are halogens/) You couldn't forge anything out of that. It burns up. My guys use resin to dissolve the gold. But burn up the gold getting it out. Same deal on the arsenic / acid then put into charcoal. How to get it out of the charcoal without burning it up. I have a prospector playlist that has it if you can't find David Hudson. Yellow metal of gold is AU2. AU is white or black or green and possibly clear , depending on how it is annealed. It's a rabbit hole bud. Thanks for your great videos
Have you ever try to smelt down a used cupel?
Could you tell us how much money was spent on raw material to smelt the tiny beads
is there any way to recover the lead, or is it gone forever?
What brand of Styrofoam cups do you use? The ones I get from Starbucks have a cardboard diaper, must be because they are so hot.
love your video m8 keep them coming 😁
how did you start doing this. What if a young fool like me would like to start refining....where do I start and does it require any certification?
Be interesting to seem the same experiment with a better concentrate sample from another smelt where you get a few grams or more from each half.
Hi Jason, great video. Why not part the gold from the silver using nitric acid? Thanks! Dave
Lead is highly oxidized. It will take a lot of material to restore it. Is it taken into account?
Jason is our TH-cam high profile chemist.
I do believe in REFINING. dunking the lead back in. But with all the sodium and heat.....you can triple your losses. What if you didn't dunk it in. Use 30g lead each time. Try a borax control smelt and compare?
I don't think there is a "best" flux or method. I think it all depends on the chemistry of the ore and as that changes so will the flux. There's likely a very good middle ground/average but I doubt there is a one size fits all recipe.
What the heck level of college chemistry did you take? Crazy amount of knowledge impressive to a financial analyst.
Great video!
Hi Jason,
I have some sulfides that I want to smelt. They’re mostly made up of Galena, Pyrite and minor amounts of Chalcopyrite. How did you determine how many moles of sodium hydroxide to use based on your cons?
How do you go about separating the silver from the gold?
How do you separate out the silver from the gold?
now i heard you mention that one 2NaOH melts lower now what if you combined the methods so half 2NaOh and half Na2O3
Now I see why I should of paid attention in chemistry!
How does the cost of the flux and fuel that you use compare to the value of the refined metal?
What would you do with ore that has weathered and you suspect is mostly iron (little to no sulfides)? Does it hurt to do the same process?
So it’s worth saving the 2nd concentrate’s to possibly leach later in a test.?
Hi Jason , I just referred you to
Minor 49er , looking at a mine he has been into recently, looking at the walls color looked really good I mentioned to him to take samples, I'm sure he needs help with that kind of stuff .. I instantly thought of you... hope he takes my advice and contacts you...
R/Steve
I don't go to sites that say Text me at another place.
I think it's a scam. Pioneer Pauley had the same problem with that...
So sorry look for another sucker.
Hi Jason, the only way to do an accurate test is to have samples with known quantities in them. Then you can measure after the test and see how much has been recovered. Does it help to pour the molten metal/flux quicker in to the test mold? For some reason it seems to me that more flux flowing with the metal rather than less flux would recover more metal. How porous does the crucible get? It looks rough making it tougher to pour from.
The recipe for Platinum smelt is 10 to one borax. No sodium. It burns platinum I am seriously squinting at the sodium I am using.. How much burned up the exhaust? I heard it may hurt the silver too. Gold? Who knows? i think it has to do with the boiling point of sodium.sodiom bicarbonate boils a 2912 F
Can you recover the lead from the used Cupels
I thought you had three samples. It would be interesting to see the scatter.
Asking just out of curiosity, not a criticism, but isn't this chemistry well-known after hundreds of years of recovering gold from ore? Or have large operations all done something different (like cyanide leaching) so this isn't as well understood as it could be?
Enjoy the videos!
Every ore behaves differently.
With your process can you turn 14k gold to pure gold?
NaOH is green. no co2 released.
Hey Jason, why do you not use an induction coil to get up to temp faster? Is it just cost?
Induction only works on ferromagnetic metals.
@@Rorschach1024 That's incorrect. Anything can be heated at high frequencies.
The difference between soda ash and lye might be fuel consumption.
Zipline to help carry bags of ore back down the mountain
Sometimes I just space out while watching your videos.
Do you ever do a test run on your Slag?
How long does it take to finish in the furnace? Thanks sharn
Of course my luck lately.. I was the 666th thumbs up..🙄.. always enjoy your videos Jason keep up the great work.🍻
If you could try to leave the nails out? something about gold riding a iron horse
Can You do the philosophical stone?
Jason: did you know you can make your on alkali sodium products in your furnace?
Just thought I would mention that....
Like it👍👍👍
Was that dans 2nd’s?
At scale, 5% more precious metals from one method over the other seems like a significant amount to me.
Wondering if you can reclaim the lead from the used cupel? I reclaim lead oxide (dross) back to pure pb using carbon (sawdust) to remove the O atoms releasing Co2 in my bullet casting operations
I remember that Jason has done that in a previous video.
Crushed the cupels to dust and smelted with charcoal i think.
Best and simplest iju
Interesting to see some original ore. I have a vein of sulfides that is easy to get to and assays 0.08/ton on the relatively clean sulfides. Have always wondered if that one is able to be made into some profit.
How wide is the vein? Might watch hardrock university to answer that question.
How many onces are on 1% of a ton? 2 pounds? so 24 troy oz? Daddy needs a new pair of shoes.
@@paulcoover9197 1 percent of a ton is 20 lbs but the grade reported is 8/100s of an ounce per ton or about three grams. With buyers margin you could figure 120 per ton which might be great if a huge volume and a big company could be intrested. But for a small miner diging a ton a day 120 if perfect recovery minus costs is just about wages
I like your "napkin math"...
Hiya Jason
Money grave, but thats ok the point was to show whats happen. Greetings from Germany
Magic moments still 😎
Enjoyed
That came to close to 200g/ton?
Depending on a lot of other factors, I could still make munny at that rate... ~( 'w')/
Fun with chemistry.
sodium burns up Platinum. How about silver and gold? you need a reducing atmosphere
Keep the oxygen out. old timers used grease and wheat flour or charcoal.