From Bailey McCrea <bailey@ican "net>
To Don Strachan <donstrachan@renfrew
Sent. Tuesday, January 15,'2A02 9:21 PM Mindamar
Hello Don
Finally found time to get the Mindamar story down!
This excerpt was taken from 'The Criteria For selection To The Canadian Mining Hall Of Fame, 1993'. Dad had started Sigma Mines Ltd, Indian Molybdenum Ltd, Campbell Red Lake Mines Ltd, Mindamar Metals Corp Ltd, and Dome Petroleum Ltd [oli], all part of Placer-Dome today before he died.
Jim McCrea [Dad}had died in 1953 at age 55.
Mindamar:
One of Dome's ventures was Mindamar, an old Zinc-lead-copper property which lay fofty miles south of Sydney at Stirling, on Cape Breton Island in Nova Scotia. On this site stood the Stirling mine, which had been in business for many years, but had closed during the depression of the thirties.
Dome Exploration (Canada) engineers and geologists. decided to investigate the mine in 1949, by incorporating a Dome Exploration,'Mindamar metals Corporation', and obtaining the mineral rights from British Metals. McCrea was interested in expanding Dome into the base metals as well as continuing with gold and silver.
Values, both indicated and probable reserves showed 780,000 tons, estimated at 8 percent (160 lbs) zinc, 1.8 percent (36 lbs) lead, 0.9 percent (18 lbs) copper,Z.00 ounces of silver and 0.03 ounces of gold in each ton of ore. See lower actual head grade values farther on in this little talk!
James McCrea, President of Dome, also became President of Mindamar and promptly arranged for the sale of zinc concentrates to the United kingdom Ministry of Supply for four years, and of copper-lead concentrates for two years to a smelter in the States, due to knowing ‘Contacts” he had while he was a dollar-a-year man during the war. (There were a group of men who performed critical work during the war for the Canadian Prime Minister, with pay to them, being one dollar for a years work [they all had other paying jobs, Don]. McCrea had the job of secretly evaluating specialty metals inventory of Canadian Geological Resources during the war years to be mined when necessary during the war; he probably got British metals info on the Stirling mine at this time and followed it up later after the war ended).
The company established a town site with 64 homes and a school for 80 children of the work force, and the mine began operating with 240 men in 1952.ln its first year, Mindamax produced "at a profitable level" but encountered metallurgical difficulties in maintaining a steady rate of recovery from the difficult ores fed to the mill. McCrea put the eminently world known metallurgist, C. W. Dowsett to the problem, but this gentleman died part way through the first year of operation before the difficulty could be solved for the flotation troubles.
McCrea himself died the year after, of a massive heart attack. The new President did not have the 'want' to keep Dome in base metals and so the metallurgy problem was not completely solved. Low recoveries means not enough monies made to pay off mine-site costs and smelter charges as well as give a return to Dome for the monies [capital] invested in putting the mine into production.
When the zinc contract ended, in April, 1957, the Mindamar mine was closed. (They seemed to be in trouble during the last two years as there was no copper-lead contract unless they had been able to extend the copper-lead contract). [Don, different info below shows that contracts were found; it was selling problems that closed the mine]. During the mine's life it processed way more ore than the original reserves of 780,000 Tons, actually close to 1,100,000 Tons.
[Don, if Dad had lived Dome would have stayed iu the base metal mines as well as gold mines. C. W. Dowsett was my Grandfather on my Mothers side He, many times, ran complex base metal mines and smelters in Rhodesia before coming in to help with Mindamar. His son Kenneth Dowsett, also a metallurgist wasn't up to him and so the problem wasn't solved to completion. Not many people knew how to get rid of the talc problem that Mindamar had].
My brother. Charles, even attempted to attack Mindamar's dilemma by taking it on for his Thesis for his Bachelor of Applied Science degree in mining.
Here's his suggested work, but it came too late, completed in April, 1955 to make much of a difference on profits, even if a tried-and-true self-taught mill super wanted to use information from a new graduate from a university with little practical milling knowledge, even if Charles was backed by a flanks' of professors:
'If the talc is sufficiently high in content to blind all sulphide flotation, then the talc should be removed by pre-flotation. Being soft it can be freed at a coarser mesh. therefore two-stage grinding would be advantageous with talc being floated between stages.
No collector reagent is to be used, depressants yes, such as cyanide - zinc sulphate, etc, keeping the zinc sulphates, iron sulphides and copper and lead sulphides from floating with the talc. [This is a delicate job, Don].
Use pine oil - only in sufficient quantity to keep forming a voluminous talc froth. Density should not be over 25%o solids [this causes trouble in the secondary grinding unless classifiers or thickeners are used; the mill super actually used cyclones].
Noakes reagent is added in the cleaners (a reaction product between quicklime with phosphorous penta sulphide, very sensitive mixture); this deadens all sulphides and lessens their chance of floating in the Talc cleaning circuits. Throw out the final talc concentrate to tails.
[What's floating or flotation? In a tank there is an impeller; let fine solids and water, a slurry, enter in one side and exit out the other side; and mix it by the impeller stirring blade with holes to let air go down its shaft. Bubbles are made which rise to the surface of the thin slurry. Some particles in the slurry stick to the bubble and some don't depending on what chemicals are used, yaaaay, a separation; let the bubbles overflow the front of the tank and catch bubble-carrying mineral for further work on it, the slurry leaving the tank going on for other work].
There may not be a perfect elimination of talc, but any remaining in the circuit will be readily held in control with suitable talc depressants'. [Now after most of the talc has gone continue on floating the payable concentrates. This should give good grades with high recoveries]. Charles says that the mine treated 675 to 700 TPD, an accomplishment for the then Mill Superintendent, W. F. Galloway, who gives the following info:
[Large feed variations occurred which should not occur with any mine with underground grade control that can be controlled.
The mill super mentions that “We have no complete analysis of the ore. Highly varying ore conditions, hourly, such as we encounter here, do not expense a complete analysis being run. However, a typical analysis, say for a month, has the following incomplete analysis:
Zinc - 5.7 to 6.54% as sphalerite
Lead - 1.33 to 1.6% as 'WOW' [my exclamation sound] as galena, minor other sulphates, and in addition 'WOW' carbonates
Copper - 0.65 to 0.75% as nice chalcopyrite, difficult tennatite and bad tetrahedrite
rage J or o
Iron - 7.00 to 8.00% as nice pyrite, and minor oxides; no bad phyrrotite
Sulphur – 11-12%
gold - 0.03 to 0.04 /T as free. very bad [lost to cyanide disolving]. and with copper/lead minerals.
Silver - 1 .70 to 2.30 oz/Ton as free. very bad {lost to cyanide disolving]. and with copper/lead minerals.'
‘Our Coper-lead (allin one) concentrate obtained at a concentration ratio of 25-28:1
Contains
Bismuth at 0.08 to 0.09%
Arsenic {ugh,ugh} 0.90 to 1.0%
Antimony at 4.0 to 0.5%
Cadium at 0.25% {should be in zinc concentrate to get any value},
Manganese {ugh} at 1.0%
Aluminum oxide at 0.2%
Calcium oxide at 1.1%
Tin at 0.01%
{all previous giving large penalties on a ton of concentrate {less monies paid on each ton shipped}
:as well as copper, lead, zinc [ugh], and iron'
All this ore was lousy to work with, Don.
Notice the Mill Super made no mention of Talc. This fellow did a stupendous job with what he had to work with!!!
Charles mentions something different in 1955; the zinc concentrate goes to smelters in the United states and the copper-lead concentrate went to Halifax by rail and loaded on ships for smelters in Europe. Possibly Dad's contract had run out and the new President obtained new ones??
Charles's conclusions follow:
The report of the character of the ore stated that the sulphides and the gangue [iron pyrite as well as this new stuff called talc] were "Intimately Mixed".
The problem of making a clean separation of the sulphides among themselves as well as from the gangue material certainly is difficult.
If the ore were ground to 100% minus 325 mesh [very fine baby powder] [mill at this time running on70% minus 200 mesh, like fine sand], as much as 29% of the zinc is still attached with the other sulphides.
Too, there is another adverse effect that fine grinding will have on flotation which is the oxidation of the lead sulphides; fine grinding exposes a very large surface area to oxidizing agents; when oxidized, the lead sulphides respond very poorly to flotation, resulting in high tailings losses [Mill Super put in cyclones (fast time) replacing a thickener (slow time) to eliminate this problem].
Too fine a grinding makes mineral separation very difficult due to sliming [100% minus 400 mesh] and great loss occurs to the tailing pond instead of the concentrate bins.
If ground too little, the sulphide particles are still joined together, defying separation by flotation, giving low unsalable grade concentrates.
Mindamar Mill for 1954,,
Copper-Lead Concentrate Grade
Lead at 24.6% [should be 65% in this day-and-age, but I have to remember this is a mixed concentrate, not a pure lead conc]
Copper at ll.33% [could be better; here I have to remember it is in with lead sulphides and carbonates]
Its recovery was 70% of lead and 68% of copper [very good for this difficult ore but lousy saleable product for keeping contracts].
Lead recovery losses ended up with l0% to the zinc conc and 20% to tails; and Copper losses ended up with 9% in the zinc conc and 23% to tails.
Zinc Concentrate Grade :
Zinc at 54.3% [very good grade]
It recovery was 76 % [for payable returns on heads grade of 5.7% Zn iit should be 89 ta 91% recovery in today's mills].
It was found that 8% of the zinc was in the copper-lead concentrate and that 16% ran out to the tailings pond.
Charles says: Unfortunately every mine has to throw values to the waste dump/tailings. This is due mainly to the fact that because of certain metallurgical problems it will cost more than it is worth to extract the remaining metal. At Mindamar a talcose gangue and close admixing of the values makes these problems, here, some of this country's most difficult.
In a nut-shel, Don, minerals processing metallurgy was the killer; but
Aiso I think the ore reserves were probably economically eliminated by passing them through the mill [doesn't mean that another ore body could be found nearby?????} not strictly and all blamed on the new president of Dome.
Now. a nice small chemical dissolution smelter on the tailings !!!: now that's a thought. The rich tailings product has already been mined and ground up! That part of costs have already been spent. chemical plant like Yava Mines might have. One could get some good metal saleable products as metal powders. not concentrates and there is over a million tons of the stuff!!!
Hope your relatives in Framboise might find this interesting.
Bailey
To Don Strachan <donstrachan@renfrew
Sent. Tuesday, January 15,'2A02 9:21 PM Mindamar
Hello Don
Finally found time to get the Mindamar story down!
This excerpt was taken from 'The Criteria For selection To The Canadian Mining Hall Of Fame, 1993'. Dad had started Sigma Mines Ltd, Indian Molybdenum Ltd, Campbell Red Lake Mines Ltd, Mindamar Metals Corp Ltd, and Dome Petroleum Ltd [oli], all part of Placer-Dome today before he died.
Jim McCrea [Dad}had died in 1953 at age 55.
Mindamar:
One of Dome's ventures was Mindamar, an old Zinc-lead-copper property which lay fofty miles south of Sydney at Stirling, on Cape Breton Island in Nova Scotia. On this site stood the Stirling mine, which had been in business for many years, but had closed during the depression of the thirties.
Dome Exploration (Canada) engineers and geologists. decided to investigate the mine in 1949, by incorporating a Dome Exploration,'Mindamar metals Corporation', and obtaining the mineral rights from British Metals. McCrea was interested in expanding Dome into the base metals as well as continuing with gold and silver.
Values, both indicated and probable reserves showed 780,000 tons, estimated at 8 percent (160 lbs) zinc, 1.8 percent (36 lbs) lead, 0.9 percent (18 lbs) copper,Z.00 ounces of silver and 0.03 ounces of gold in each ton of ore. See lower actual head grade values farther on in this little talk!
James McCrea, President of Dome, also became President of Mindamar and promptly arranged for the sale of zinc concentrates to the United kingdom Ministry of Supply for four years, and of copper-lead concentrates for two years to a smelter in the States, due to knowing ‘Contacts” he had while he was a dollar-a-year man during the war. (There were a group of men who performed critical work during the war for the Canadian Prime Minister, with pay to them, being one dollar for a years work [they all had other paying jobs, Don]. McCrea had the job of secretly evaluating specialty metals inventory of Canadian Geological Resources during the war years to be mined when necessary during the war; he probably got British metals info on the Stirling mine at this time and followed it up later after the war ended).
The company established a town site with 64 homes and a school for 80 children of the work force, and the mine began operating with 240 men in 1952.ln its first year, Mindamax produced "at a profitable level" but encountered metallurgical difficulties in maintaining a steady rate of recovery from the difficult ores fed to the mill. McCrea put the eminently world known metallurgist, C. W. Dowsett to the problem, but this gentleman died part way through the first year of operation before the difficulty could be solved for the flotation troubles.
McCrea himself died the year after, of a massive heart attack. The new President did not have the 'want' to keep Dome in base metals and so the metallurgy problem was not completely solved. Low recoveries means not enough monies made to pay off mine-site costs and smelter charges as well as give a return to Dome for the monies [capital] invested in putting the mine into production.
When the zinc contract ended, in April, 1957, the Mindamar mine was closed. (They seemed to be in trouble during the last two years as there was no copper-lead contract unless they had been able to extend the copper-lead contract). [Don, different info below shows that contracts were found; it was selling problems that closed the mine]. During the mine's life it processed way more ore than the original reserves of 780,000 Tons, actually close to 1,100,000 Tons.
[Don, if Dad had lived Dome would have stayed iu the base metal mines as well as gold mines. C. W. Dowsett was my Grandfather on my Mothers side He, many times, ran complex base metal mines and smelters in Rhodesia before coming in to help with Mindamar. His son Kenneth Dowsett, also a metallurgist wasn't up to him and so the problem wasn't solved to completion. Not many people knew how to get rid of the talc problem that Mindamar had].
My brother. Charles, even attempted to attack Mindamar's dilemma by taking it on for his Thesis for his Bachelor of Applied Science degree in mining.
Here's his suggested work, but it came too late, completed in April, 1955 to make much of a difference on profits, even if a tried-and-true self-taught mill super wanted to use information from a new graduate from a university with little practical milling knowledge, even if Charles was backed by a flanks' of professors:
'If the talc is sufficiently high in content to blind all sulphide flotation, then the talc should be removed by pre-flotation. Being soft it can be freed at a coarser mesh. therefore two-stage grinding would be advantageous with talc being floated between stages.
No collector reagent is to be used, depressants yes, such as cyanide - zinc sulphate, etc, keeping the zinc sulphates, iron sulphides and copper and lead sulphides from floating with the talc. [This is a delicate job, Don].
Use pine oil - only in sufficient quantity to keep forming a voluminous talc froth. Density should not be over 25%o solids [this causes trouble in the secondary grinding unless classifiers or thickeners are used; the mill super actually used cyclones].
Noakes reagent is added in the cleaners (a reaction product between quicklime with phosphorous penta sulphide, very sensitive mixture); this deadens all sulphides and lessens their chance of floating in the Talc cleaning circuits. Throw out the final talc concentrate to tails.
[What's floating or flotation? In a tank there is an impeller; let fine solids and water, a slurry, enter in one side and exit out the other side; and mix it by the impeller stirring blade with holes to let air go down its shaft. Bubbles are made which rise to the surface of the thin slurry. Some particles in the slurry stick to the bubble and some don't depending on what chemicals are used, yaaaay, a separation; let the bubbles overflow the front of the tank and catch bubble-carrying mineral for further work on it, the slurry leaving the tank going on for other work].
There may not be a perfect elimination of talc, but any remaining in the circuit will be readily held in control with suitable talc depressants'. [Now after most of the talc has gone continue on floating the payable concentrates. This should give good grades with high recoveries]. Charles says that the mine treated 675 to 700 TPD, an accomplishment for the then Mill Superintendent, W. F. Galloway, who gives the following info:
[Large feed variations occurred which should not occur with any mine with underground grade control that can be controlled.
The mill super mentions that “We have no complete analysis of the ore. Highly varying ore conditions, hourly, such as we encounter here, do not expense a complete analysis being run. However, a typical analysis, say for a month, has the following incomplete analysis:
Zinc - 5.7 to 6.54% as sphalerite
Lead - 1.33 to 1.6% as 'WOW' [my exclamation sound] as galena, minor other sulphates, and in addition 'WOW' carbonates
Copper - 0.65 to 0.75% as nice chalcopyrite, difficult tennatite and bad tetrahedrite
rage J or o
Iron - 7.00 to 8.00% as nice pyrite, and minor oxides; no bad phyrrotite
Sulphur – 11-12%
gold - 0.03 to 0.04 /T as free. very bad [lost to cyanide disolving]. and with copper/lead minerals.
Silver - 1 .70 to 2.30 oz/Ton as free. very bad {lost to cyanide disolving]. and with copper/lead minerals.'
‘Our Coper-lead (allin one) concentrate obtained at a concentration ratio of 25-28:1
Contains
Bismuth at 0.08 to 0.09%
Arsenic {ugh,ugh} 0.90 to 1.0%
Antimony at 4.0 to 0.5%
Cadium at 0.25% {should be in zinc concentrate to get any value},
Manganese {ugh} at 1.0%
Aluminum oxide at 0.2%
Calcium oxide at 1.1%
Tin at 0.01%
{all previous giving large penalties on a ton of concentrate {less monies paid on each ton shipped}
:as well as copper, lead, zinc [ugh], and iron'
All this ore was lousy to work with, Don.
Notice the Mill Super made no mention of Talc. This fellow did a stupendous job with what he had to work with!!!
Charles mentions something different in 1955; the zinc concentrate goes to smelters in the United states and the copper-lead concentrate went to Halifax by rail and loaded on ships for smelters in Europe. Possibly Dad's contract had run out and the new President obtained new ones??
Charles's conclusions follow:
The report of the character of the ore stated that the sulphides and the gangue [iron pyrite as well as this new stuff called talc] were "Intimately Mixed".
The problem of making a clean separation of the sulphides among themselves as well as from the gangue material certainly is difficult.
If the ore were ground to 100% minus 325 mesh [very fine baby powder] [mill at this time running on70% minus 200 mesh, like fine sand], as much as 29% of the zinc is still attached with the other sulphides.
Too, there is another adverse effect that fine grinding will have on flotation which is the oxidation of the lead sulphides; fine grinding exposes a very large surface area to oxidizing agents; when oxidized, the lead sulphides respond very poorly to flotation, resulting in high tailings losses [Mill Super put in cyclones (fast time) replacing a thickener (slow time) to eliminate this problem].
Too fine a grinding makes mineral separation very difficult due to sliming [100% minus 400 mesh] and great loss occurs to the tailing pond instead of the concentrate bins.
If ground too little, the sulphide particles are still joined together, defying separation by flotation, giving low unsalable grade concentrates.
Mindamar Mill for 1954,,
Copper-Lead Concentrate Grade
Lead at 24.6% [should be 65% in this day-and-age, but I have to remember this is a mixed concentrate, not a pure lead conc]
Copper at ll.33% [could be better; here I have to remember it is in with lead sulphides and carbonates]
Its recovery was 70% of lead and 68% of copper [very good for this difficult ore but lousy saleable product for keeping contracts].
Lead recovery losses ended up with l0% to the zinc conc and 20% to tails; and Copper losses ended up with 9% in the zinc conc and 23% to tails.
Zinc Concentrate Grade :
Zinc at 54.3% [very good grade]
It recovery was 76 % [for payable returns on heads grade of 5.7% Zn iit should be 89 ta 91% recovery in today's mills].
It was found that 8% of the zinc was in the copper-lead concentrate and that 16% ran out to the tailings pond.
Charles says: Unfortunately every mine has to throw values to the waste dump/tailings. This is due mainly to the fact that because of certain metallurgical problems it will cost more than it is worth to extract the remaining metal. At Mindamar a talcose gangue and close admixing of the values makes these problems, here, some of this country's most difficult.
In a nut-shel, Don, minerals processing metallurgy was the killer; but
Aiso I think the ore reserves were probably economically eliminated by passing them through the mill [doesn't mean that another ore body could be found nearby?????} not strictly and all blamed on the new president of Dome.
Now. a nice small chemical dissolution smelter on the tailings !!!: now that's a thought. The rich tailings product has already been mined and ground up! That part of costs have already been spent. chemical plant like Yava Mines might have. One could get some good metal saleable products as metal powders. not concentrates and there is over a million tons of the stuff!!!
Hope your relatives in Framboise might find this interesting.
Bailey