In a broad sense, there are basically two types of way that gold is recovered. Gold around the world is either found in hard rock deposits or as placer deposits.
Hard rock, or “Lode” gold is still contained within ore, and various methods are used to extract the metal from the rock that surrounds it. Placer gold on the other hand occurs when natural erosion has released the gold from its host material and the gold is now a separate piece, whether that be a small speck of gold dust or a large gold nugget.
Where Each Type of Gold Occurs
In most mining districts you can find a combination of hard rock gold and placer gold sources. During the early gold rushes of the 1800s, it was common practice for miners to flock to an area and quickly start prospecting for the easy-to-get placer gold in rivers and creeks. These were the locations where millions of years had concentrated gold into rich pockets and paystreaks, and a miner could often recover pounds of gold using nothing more than a gold pan.
Generally as the placers would slowly become exhausted, miners would begin tracing the source of the gold and begin developing hard rock mines. These mines were more labor-intensive than placer mining, but if a rich gold vein was located they could be exceptionally rich to work.
The prevalence of placer gold vs. hard rock gold varies significantly depending on the area. In some states like California
, most of the gold that has been found comes from placer deposits. However, other states like Nevada
and South Dakota
, the vast majority of gold that has been mined there has come from hard rock.
Cost of Extraction
Both types of gold mining occur today, but you will notice that this is highly dependent on who is mining the gold. Today, nearly all small-scale prospectors focus their efforts on placer gold that can be recovered from mining methods like panning
, and dredging
. This has a lot to do with the ease of recovery and the cost associated with it.
Hard rock mining is expensive. Unlike placer gold that can be found with just a simple shovel and gold pan, extracting gold from ore takes considerable start-up costs. Nearly all hard rock gold mines in the United States today are operated by large companies that have the money needed to invest in the initial costs. Tens of thousands of dollars often needs to be spent before a hard rock mining operation even starts production.
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Variation in Hard Rock Gold Ores
Hard rock gold sources are not created equal. Each source of gold will vary considerably.
The amount of gold per ton of ore is generally how the value of a hard rock ore body is evaluated. Some high-grade free-milling ores that have visible gold veins running through quartz may run as high as an ounce or more in gold for each ton of rock, however most gold ores are considerably less than that.
Commercial mining operations can mine lower-grade ores due to the huge volumes of material that they are able to process at one time. Even ores that only have just a gram of gold per ton of rock can be mined profitably in some cases. Some of the biggest and richest open-pit mines in the world, like those found within the Carlin Trend deposits
of Northern Nevada, are producing only low-grade ores.
Also Read: Crushing Ore Samples for Gold
Placer Gold Deposits
Most miners look for placer gold in creeks and rivers, where it has been eroded from the surrounding mountains and deposited within paystreaks in the gravel. These are great places to look for gold and you can still use simple placer mining methods to recover nice gold from them.
However, there are other types of placer gold deposits that you can mine that have good concentrations of gold that are not located in places that you would traditionally look for it. Placer deposits can be found in beach sands or as bench deposits high above today’s current waterline. We take a more in-depth look at some of these locations in our article ‘Types of Gold Placers
Hard Rock vs. Placer Mining – Which is Better?
For the average gold prospector, focusing on placer gold sources is probably going to be most productive. The gold is easier to get to using traditional mining methods, and the cost of extraction is considerably less.
Still, that is not to say that hard rock mining is out of the question, even for the casual prospector. Someone who locates a good high-grade source of hard rock gold can use a rock crusher to extract gold from the rock and may still be able to mine profitably.
In fact, some successful prospectors I have talked to believe that small-scale hard rock mining may become more productive for them than placer mining in the future, as the easily recovered gold is “mined out” and only less-rich deposits remain.