Step 2 – Sampling Your Gold Mine
First things first – Define your ore body.
Most people think of finding gold nuggets. The truth is that very little comes from nuggets – nearly all newly mined gold comes from ores mined from the natural hard rocks that contain gold in tiny, even microscopic particles. The following are some examples of gold ore.
When searching for or finding gold ore it is good to remember that, gold deposits in the western United States are most frequently found mixed within iron ore deposits so look for dark and rust colored iron ore on the rock walls of the mine. The old Spanish miners would say “Gold rides an iron horse.” The weight of gold, silver, copper and platinum are similar enough that often you can find some combination of all of the “four metals” mixed together. That is especially true in the West, where the mountains are new enough that other forces haven’t separated the four metals.
You will want to chip out the iron ore rock and crush it, so that it can be separated. Iron ore accounts for approximately 5 percent of the Earth’s crust. Iron rusts easily when exposed to oxygen and gets it’s redish hue. Iron ore is commonly found next to quartz. In the picture with the white quartz vein you can see the dark red/brown iron ore, just above the quartz. When quartz and iron were formed they cooled at a different temperature and separated. You can think of it like cow’s milk. The cream floats to the top and separates from the milk, but both are found right next to each other. If you were to mine this vein you would chip out the white quartz and the iron ore. Because, as noted in the picture, not all of the iron ore has completely separated from the quartz and small pieces of iron ore are found encased in the quartz. Also note the dull, grey, thin, line below and above the quartz. This is where silver will be found. When finding gold ore remember that concentration of gold and silver will vary so it’s a good idea to gather samples from different sections of the mine so that they can be assayed. Fill a five gallon bucket from different section of your mine. Make sure to label the bucket and the section of the mine and either crush the ore yourself or get it assayed.In this photo you can easily see the vein of iron ore. You would want to chip out the whole vein for processing. The highest concentration of gold will be found on the right (the darker brown section). The red in the middle of the photo indicates a higher concentration of iron. Iron will separate from the gold while panning or sluicing. The density of gold is over twice that of Iron. A gallon of water weighs a little under 8.4 pounds. The same volume of Iron would weigh just under 65.7 pounds, and the same volume of gold would weigh just over 161.2 pounds. Sluicing gold is effective because gold is over 19 times denser than water and over twice the weight of Iron. The table below can give you a good idea of the comparison of different common metals.
Densities of materials
Density information courtesy of Hoadley, Rick – http://www.coolmagnetman.com 1998-2012
In this photo the dull black or dark gray area (large circled blue area on the left of the picture) is a combination of silver lead and zinc. Again the red rock gets it’s color from oxidized iron. Gold can be found mixed with the iron, but the higher concentration of gold will be found in the brown rock, which is mixed in with the black rock. Also next to the yellow sulfur you can see some brown rock (circled in blue) and that rock also shows evidence of gold.
The photo with the black glove is another good example of iron ore that cooled and separated frome the quartz. The iron ore separated from the quartz when it cooled, but is found all around it. You would want to pull out all of the rock including the quartz for processing. Sometimes the gold is in a finely divided state, sometimes it’s found in larger sizes, such as nuggets, grains, scales, plates, threads and wires in quartz rock.
Sometimes gold is found in tiny specs scattered through slate and some sedimentary rocks like limestone. The gold was placed there by the flow of heated and mineralized waters. Sulfur is often a transporter of gold. So it’s not surprising that native gold is also very commonly found within sulfide minerals such as pyrite. Pyrite can contain up to 30% of gold content. Iron pyrite acts as a reducing agent. This means that the pyrite won’t bond with the gold. So, whenever gold is found in pyrite, it is always present as free milling gold. This last picture shows a yellow layer of gold between quartz. Also note a dark gray vein of lead and silver. You would want to chip out the whole vein from the rock.
After you have defined the ore deposits start taking samples
Once you have found valuable ore pockets, you should determine which direction they headed. Sometimes you can see them running along the spine or the ribs of the mine. Sometimes it’s a little more obscured. Using your rock hammer, start breaking out rock around the ore deposit. Work around it until you find the edges of it, these will usually be bordered by quartz. Take a can of spray paint along and define this lode, either with a name or a number. A big #1 will usually do the trick.
Work the ore body.
Now that you have defined the edges, start working away at breaking up the ore between those edges. This is the fine work. Keep your bucket handy. You want to put all of the ore from this section into a single bucket. A good 5 gallon bucket from Home Depot should do the trick. Fill this bucket up with your ore from this pocket. DO NOT MIX ORES. Mark your bucket to correspond with the deposit ID defined above; A big #1 for first deposit a #2 for the second and so on. Find different sections of ore bodies in the mine. Mark them off and fill another bucket with ores. Do this until you have 3-5 buckets of ore from different sections in the mine.
Your next step is to assess the quality of the ore
This can be done one of two ways:
- The first is the most simple; take your buckets to an assayer. Give him the ore, tell him what you are looking for, and pay for the assay work.
- Alternatively you can do this work yourself. You will need a few items, first of which is a crusher. There are all sorts of crushers from small hand held units to large industrial machines. Decide your budget and start crushing. Once you have crushed up the ore to a fine powder you have a few more options.
- Panning methods – Put some of your crushed material into a gold pan, wash it through and see how much gold you have.
- Sluice method – This is by far the most simple. Get a good sluice, a sluice is a production line for panning. It allows you to process more material and automates the separation of the gold. Gold Cube or the like will do an excellent job. Just run the material and then take out the gold. This can be done anywhere there is a water supply; on the claim, or in your backyard with a hose!
- Chemical method – There are many chemicals that will interact with gold, silver and copper in specific ways. Run the chemicals through your material and see what comes out! (GRE, Inc. can offer more assistance on this if needed).
Here are some more samples of gold ore taken from mines throughout the western United States. This video will give you a good idea of what to look for inside your mine.
After you have tested the ores it is time to start working your mine, which is what we will learn in the next section.