First. Great pictures, it is much easier to determine what a person is talking about with a good picture.
Second. I think you are doing exactly what you should be doing in your situation (in my opinion). You are doing your sampling and mapping, becoming familiar with your workings/ore type/grade etc. without breaking the bank.
It sounds to me like your strategy is as follows (just to clarify and reiterate): Sample and map to determine average grade and ore character. Determine what “high grade” looks like and identify places in your workings that may contain high grade (i.e. brecciated portions of the vein, vein intersections, Jogs or turns in the vein, etc.). Again this is exactly what I would be doing in your situation.
My next question for you is: What are your goals for the property and what do you think your next step may be?
I am going to make an assumption here and assume you plan to open up some of the old workings to access the vein and begin small scale mining again with a small crew of your own or hire someone to work for you. The other option you may be thinking about is proving up the property with samples and maps and then trying to promote/sell/lease the property to another company.
Lets say you are going to open up the old workings and begin mining and milling on site on a scale of 1-10 tons/day. If you have found a higher grade portion of the vein which has some potential to produce tons this is where I would start.
I am going to take a little side trip here and talk about mining costs. I work for a small mining company with 3 employees and I will try to summarize our mining costs to get you in the ball park to determine if your ore is of sufficient grade to warrant mining.
We have a 3 man crew working 12 hour days 6 days a week. We average somewhere between 60-90 days/year due to snow pack late in the summer and snow early in the fall. Our mining costs are approximately $120,000/season or around $2,000/day. This is just our mining costs this does not include trucking, crushing, milling etc. We produce around 500 tons/year, which brings our mining costs to $240/ton. I think an average milling fee for on site milling would be around $150/ton. So to review lets say it costs $250/ton to mine $150/ton to mill and make a con, and another $100 per ton (of bulk ore produced not $100/ton to refine the cons) for final refining to produce a saleable product. Our total mining costs are 250+150+100=$500 per ton plus or minus.
Also keep in the back of your mind the milling and concentrating process will only recover, let’s say, 90%.
This means we need at least $550/ton of values to break even (considering 90% recovery). So during your mapping and sampling process keep these numbers in mind.
Now I don’t want to discourage you, I just want to make sure we all (not just aumbre, but everyone reading this) keep in mind the costs involved in small scale mining. These prices may vary depending on the site, width of vein, mining method etc, but this is a good starting point for getting something down on paper. (There is another good post here called “hard rock production costs” which has loads of great info about mining costs)
I am getting way off track here and will come back to your original question: “Would this be a good location to bulk sample”. I would say that if you think this is an area with potential for ore development, the ore grade is promising (i.e. $550+/ton), and there is enough reserves to warrant starting a mining operation then, yes this would be an area to bulk sample.
Even if this area doesn’t meet one of the above criteria I would still say consider bulk sampling. Then you will know if the ore is amenable to gravity concentration or does it need to be shipped off to a mill hundreds of miles away (huge costs). Most big mills with need a minimum amount of ore before they will consider processing (1000 tons is a number I have heard for Kinross’s Kettle River mill in Republic, WA). So bulk sampling will answer some key questions for you in how you proceed with your project, even if you are still on the fence about other questions.
A few questions for you:
Have you tried hand crushing and panning to determine free gold?
I have used to following tests for free gold in the past on ore samples: If you can determine what high grade ore looks like, take a sample of say 5-10 lbs of high grade ore. Weigh the sample accurately (to a 1/10th of a lb.) and hand crush the rock to a powder (it takes a while, but it’s worth it). Weigh the gold that’s recovered and using the weight of the gold and the weight of the original sample you should be able to determine (very roughly mind you) your oz/ton in that sample. Now that is a long explanation to make this point. If your high grade samples assay 1-5 oz/ton and you can only pan .1-.2 oz/ton from the sample then it doesn’t look good for gravity concentration of free gold. However, this doesn’t mean you couldn’t make a gravity concentrate of the sulfides and refine them to extract the gold, it just means your ore does not carry a high percentage of free gold. You could even expand the experiment to assay and screen the panning tailings (crushed quartz) and assay the panning cons (sulfides and gold) and this will tell you something about liberation and percent recovery if the sulfides are removed from the quartz. These are all very rough calculations and should be used again to get a ball park figure.
What does the old literature say about your mines history? What grade did they average? What vein thickness? Where there ore shoots and barren areas or was the material fairly consistent in grade?
The old mining records/literature can be invaluable information when trying to open up an old mine.
Do you have an estimate on the potential reserves left in the current workings?
I think I have rambled on plenty for one post and hopefully have given you something to stew on for a while. I think you project definitely has potential. If the old timers worked it to the extent you say, there must have been something worth getting. Keep us posted and I would very much enjoy to hear about anyone else’s projects they have going or old workings they own.
Jason GaberMt. Baker Mining and Metalsmbmmllc@gmail.com