Geology and stories from the past
Weathering, Erosion and Placers
April 2017
The big interest to prospectors thinking about the effect of erosion is not what might happen long into the future, but what they might find in the rivers later this summer when the water levels go down.
The big interest to prospectors thinking about the effect of erosion is not what might happen long into the future, but what they might find in the rivers later this summer when the water levels go down.
Diary of a Diamond Prospector
April 2017
I couldn’t wait to get started. With no field budget, an assay budget of $100/year, a 1975-Ford Bronco that was a road hazard, a gas card, a topo map and full support of the director, I headed to the State Line district near Tie Siding along US Highway 287 to begin mapping kimberlite.
I couldn’t wait to get started. With no field budget, an assay budget of $100/year, a 1975-Ford Bronco that was a road hazard, a gas card, a topo map and full support of the director, I headed to the State Line district near Tie Siding along US Highway 287 to begin mapping kimberlite.
Epithermal Gold and Silver Deposits
April 2017
Epithermal deposits form in the ground at shallow depths. They are popular with prospectors because can yield very rich deposits and they are widespread in the Western US.
Epithermal deposits form in the ground at shallow depths. They are popular with prospectors because can yield very rich deposits and they are widespread in the Western US.
All About Chalcopyrite
March 2017
…there are loads of different copper minerals, but a large number of them form first in the ground as chalcopyrite and then through the effects of weathering are changed into other minerals like malachite, cuprite and chrysocolla.
…there are loads of different copper minerals, but a large number of them form first in the ground as chalcopyrite and then through the effects of weathering are changed into other minerals like malachite, cuprite and chrysocolla.
The Goldfield Mining District -- Then and Now
March 2017
In 1983, some of the ore yielded more than 2,500 ounces of gold within 30 feet of the surface. The shoot pinched to a narrow vein.
In 1983, some of the ore yielded more than 2,500 ounces of gold within 30 feet of the surface. The shoot pinched to a narrow vein.
Nevada's Lithium Boom
March 2017
When prospecting for lithium, after confirming for macro attributes through research and field work, including examination of surface geology, the main tool is an accurate lithium assay.
When prospecting for lithium, after confirming for macro attributes through research and field work, including examination of surface geology, the main tool is an accurate lithium assay.
Calcite and Limestone
February 2017
The other distinguishing feature of calcite has to do with its chemistry. Geologists sometimes take a small bottle of dilute hydrochloric acid out into the field with them because calcite reacts with acids to make a bubbly foam.
The other distinguishing feature of calcite has to do with its chemistry. Geologists sometimes take a small bottle of dilute hydrochloric acid out into the field with them because calcite reacts with acids to make a bubbly foam.
Gangue Minerals - What Do They Tell Us?
January 2017
There are a large number of different kinds of gangue minerals, and each of them has its own tale to contribute to the story of the chemistry and geology of a deposit.
There are a large number of different kinds of gangue minerals, and each of them has its own tale to contribute to the story of the chemistry and geology of a deposit.
Prospector's Guide to Rock Breaking and Blasting
December 2016
The holes were overloaded with explosives, but I didn’t know it. I was just a green mining engineer fresh out of school and told to watch as the experienced miners set the charge.
The holes were overloaded with explosives, but I didn’t know it. I was just a green mining engineer fresh out of school and told to watch as the experienced miners set the charge.
Glaciers and Placer Gold Deposits
November 2016
It also happens sometimes that glaciers will bury valuable placer deposits. This occurs when the glacier goes over the top of an existing placer deposit.
It also happens sometimes that glaciers will bury valuable placer deposits. This occurs when the glacier goes over the top of an existing placer deposit.
The Seven Troughs Mining District
September 2016
The favorable geology of the northeastern and central parts of the Seven Troughs Range are the parts most interesting to prospectors. They are underlain by a thick sequence of Tertiary volcanic rocks, mostly rhyolites and andesites.
The favorable geology of the northeastern and central parts of the Seven Troughs Range are the parts most interesting to prospectors. They are underlain by a thick sequence of Tertiary volcanic rocks, mostly rhyolites and andesites.
Can You Recognize Valuable Ores?
August 2016
The process of recognizing ores all starts with being able to recognize some basic minerals and knowing what hard rock ore looks like in the districts where you prospect.
The process of recognizing ores all starts with being able to recognize some basic minerals and knowing what hard rock ore looks like in the districts where you prospect.
Exploring A Historic Lode Mine
August 2016
Climbing up the debris, I pointed my flashlight up a shaft ascending straight up as far as my light would shine. It was the stope of the pay shoot leading to the old tunnel above!
Climbing up the debris, I pointed my flashlight up a shaft ascending straight up as far as my light would shine. It was the stope of the pay shoot leading to the old tunnel above!
The Heavy Minerals in Your Concentrates
June 2016
The fact that mineral deposits can contribute specific types of heavy minerals is why the analysis of the heavy mineral concentrates in the streams of an area can be an important prospecting technique for finding undiscovered mineral deposits.
The fact that mineral deposits can contribute specific types of heavy minerals is why the analysis of the heavy mineral concentrates in the streams of an area can be an important prospecting technique for finding undiscovered mineral deposits.
Critical Metals: Antimony
June 2016
I’ve been taking a look at the mining and uses of a number of critical metals in series of articles, and it’s time to take a look at antimony.
I’ve been taking a look at the mining and uses of a number of critical metals in series of articles, and it’s time to take a look at antimony.
Nevada's Silver City Gold District -- Part II
May 2016...this district has had a continuous life of gold mining and milling that spans 150 plus years, and it appears that it will keep pressing on for many more years of production.
The Tombstone Silver-Lead District, Arizona
April 2016
In 1877, a prospector named Ed Schieffelin discovered silver in “the middle of nowhere” and staked two claims: “Tumbstone” and “Graveyard.” Soon a town and mining district were organized and acquired the name “Tombstone” after making a spelling correction.
In 1877, a prospector named Ed Schieffelin discovered silver in “the middle of nowhere” and staked two claims: “Tumbstone” and “Graveyard.” Soon a town and mining district were organized and acquired the name “Tombstone” after making a spelling correction.
Enrichment of Mineral Deposits by Weathering—Part II
April 2016
While both zinc and lead deposits also are enriched by the surface weathering process, in part two we will look at the enrichment process for copper and also gold deposits, and at the interpretation of leached outcrops to figure how rich the concentrated deposits below them may be.
While both zinc and lead deposits also are enriched by the surface weathering process, in part two we will look at the enrichment process for copper and also gold deposits, and at the interpretation of leached outcrops to figure how rich the concentrated deposits below them may be.
The Bawl Mill
March 2016
• Do as I say, not as I do...
• By the numbers...
• Do as I say, not as I do...
• By the numbers...
Green Valley Gold District, Payson, Arizona
March 2016
Most gold-bearing quartz veins found in the district were fracture fillings in faults enclosed by crushed quartz zones along their margins. Since the host rocks were often extensively weathered, portions of the veins stood out as positive, resistant outcrops. The gold-bearing veins ranged from a few inches wide to the vein at the Gowan mine that was as much as 12 feet wide.
Most gold-bearing quartz veins found in the district were fracture fillings in faults enclosed by crushed quartz zones along their margins. Since the host rocks were often extensively weathered, portions of the veins stood out as positive, resistant outcrops. The gold-bearing veins ranged from a few inches wide to the vein at the Gowan mine that was as much as 12 feet wide. 
