Mineral Diode Study
Last Updated: 2nd Apr 2021By Tony Nikischer
This article first appeared in Mineral News (2011) Vol. 27, No. 6, here without images:
A Hudson Institute Career Day Sparks “Mineral Diode” Study
By Tony Nikischer & Robert Fung
Excalibur Mineral Corporation
One of us (TN) recently presented the Hudson Institute’s annual “Career Day” mineral seminar at a local middle school, bringing minerals, meteorites, UV lamps, periodic tables and assorted household items to demonstrate the use (and beauty!) of minerals common in our everyday lives. “Career Days” give kids the opportunity to learn about the work that adults perform in a wide variety of professions, hopefully providing some insight into what interesting jobs and educational paths are open to today’s youngsters. It is a yearly ritual that is well received by the students and teachers alike, and in the case of the Hudson Institute’s participation with Excalibur Mineral Corp., many free mineral specimens are distributed to the students who attend the “geology” lectures. Energizing the next generation of collectors and mineral scientists is also a primary aim of our joint participation!
Not surprisingly, many youngsters were amazed at “how cool” the study of minerals could be, and their use in electronic devices created some special interest among this avid cell-phone, video game-playing crowd. It was an eye-opening experience this year, particularly because the kids were very technologically adept, but few had a real understanding of how their various electronic devices actually worked. (Welcome to my world!) While I can recollect my older brother being one of the first kids on the block to build his own “crystal radio” back in the 1950s, the electronics bugs never really bit me, and I felt woefully inadequate in explaining specific “mineral phenomena” with regard to everyday electronic gizmos. My number one, electronically-literate, Excalibur associate, Robert Fung, came to the rescue! Taking a common electronic device, the diode, and looking backwards at its mineralogical history, provided some useful information for a future “Career Day” presentation.
In the mid-1800s, scientists began experimenting with wireless signaling, an outgrowth of earlier observations and theories of electromagnetism that were being developed at the time. It was a period of explosive discovery, with names like Ampere, Faraday, Hertz, Tesla, and Rutherford all working their magic. And minerals were in the middle of it all, as radio’s origins began as “wireless telegraphy” that utilized minerals and mineral synthetics. It was Karl Ferdinand Braun who, in 1874, discovered and described the galena rectifier in his treatise Ueber die Stromleitung durch Schwefelmetalle (On the Flow of Current through Metallic Sulfides) from which the first diodes emerged. Twenty years later, Sir Jagadish Chandra Bose (Bengal) used a "cat's whisker" diode to detect radio waves, subsequently patenting the galena detector (an early radio diode) in 1901.
Although this is not a lesson in electronics, it is useful to know what a diode is and what it does, and why its discovery and use, based on conductive properties of certain minerals, became so important. In an admittedly over-simplified nutshell, a diode is a device that allows current to flow in only one direction, much like the way a gate valve in a liquid-based system works. As the simplest form of semi-conductor, diodes can act as rectifiers that convert AC to DC, and they can also demodulate the amplitude of electromagnetic waves. Many specialized diodes were developed, enabling the devices to detect and tune radio and TV signals, act as photovoltaic cells in solar energy systems, or emit visible light or infrared energy as in LED’s. Their evolution from early mineral bits to vacuum tubes to development of the transistor had a huge impact in the expansion and production of what are now everyday electronic devices.
In 1922, H.S. Roberts and L.H. Adams published an abbreviated list of mineral semi-conductors (American Mineralogist, Vol. 7, No. 8, pgs 131-136) based on their experimental observations of common “crystal detectors” made of various minerals. Of the thirteen (13) species they included, most had simple chemistry (10 of 13 had two elements, the remaining ones with only 3 elements), high symmetry (10 were isometric or hexagonal), and cleavage seemed to play no significant role. Three years later, Edgar Wherry (of wherryite fame) tested a large number of additional minerals, utilizing a copper “cat’s whisker” and a simple crystal set, finding some 75 species with radio detector properties (see American Mineralogist, Vol. 110, No. 1, pgs 28-29).
Because Wherry’s interesting experiments utilized many different species, one of us (RF) decided to attempt to duplicate the results of his “cat whisker” findings, using both a modern day oscilloscope as well as a primitive crystal radio. We selected several specimens from the Excalibur inventory (see figure 1) and prepared the first of two different experiments. In each case, a small sample, approximately 1 cm3, was trimmed from a larger specimen. A 1.2 diameter brass tube was cut into small 1cm tall sections, and was then placed on a copper circuit board. Bismuth (extracted from shotgun pellets) was heated to molten state in a crucible and then poured into the brass tube holders. While still liquid, the mineral fragment was then dropped into the bismuth-filled “vat”, and the resulting “ohmic electrode” was allowed to cool.
Figure 1, below: Table of minerals for first experiment
Bornite + Ankerite: Baltic Mine, Newton, Michigan
Bornite + Silver: Magma Mine, Superior, Arizona
Bornite + Chalcocite: Mt Con Mine, Butte, Silver Bow, Montana
Chalcocite: Unknown Locality, ex. A.E.Seaman Museum
Covellite: Butte, Montana
Galena: Ravilli County, Montana
Molybdenite: San Manuel Mine, Arizona
Molydenite: Ashdown Mine, Humboldt County, Nevada
Tennantite: Trixie Mine, Utah
Tetrahedrite: Casapalca, Peru
Zincite w/Franklinite: Franklin, New Jersey
The brass winding from an electric guitar string was used as a cat’s whisker, and it was connected to one input of our oscilloscope setup, while the other input was connected to a wire soldered to the diode base. If good contact was made, we were able to observe an asymmetrical wave deflection on the oscilloscope, and the steepness of the deflection was deemed as either poor (for low or no deflection) to fair, good or very good (for very steep deflection angle). Our results closely matched those of Wherry’s 1925 diode experiments.
In a second set of experiments, we selected additional samples and prepared “p-n junction” diodes utilizing two different minerals, connecting them to an audio amplifier, and attempting to pick up our local Peekskill radio station. We achieved a wide range of results, depending on the combinations of minerals or materials used in our diodes (see figure 2). Not surprisingly, combinations that used good conductors such as galena and chalcocite, in conjunction with synthetic quartz or synthetic zincite (from those Poland paint factory chimney specimens of some years ago), produced the best results.
So, if you are bored with collecting fancy, crystallized minerals, or you are just looking for something off the beaten path to do with your excess mineral specimens, try some of these kooky experiments. For those of you who are Ham radio operators, or for others who get radio station reception from the fillings in your teeth, yes, we have more work to do! One of us (RF) is now building a basic tuner, so that we can search for a wide range of frequencies when running experiment #2 again. And just to be complete, we’ll check tooth filling materials (silver-amalgam [Ag,Hg] and others) against hydroyxlapatite, just to confirm that the voices you hear in your head are not a result of being nuts, like we are……
Figure 2, below: Additional mineral combinations were constructed and used as p-n junction diodes. The subjective results of our local radio reception is noted in the third column.
Mineral contact #1 / Mineral contact #2 / Radio Signal
bismuth / zincite (synthetic)/ fair
Bornite + Chalcocite/ zincite (Poland, synthetic)/ good
Bornite + Chalcocite/ silicon (synthetic)/ good
bornite + silver/ molybdenite/ poor?
bornite + silver/ zincite (Poland, synthetic)/ good
bornite + silver/ silicon (synthetic)/ good
bornite + silver/ zincite(nj)/ none
bornite + silver/ chalcocite/ none
bornite + silver/ covellite / none
bornite + silver/ enargite/ none
bornite + silver/ carbon rod/ none
bornite + silver/ bronze guitar wire/ none
bornite + silver/ jumper wire/ none
bornite + silver/ galena/ none
bornite + silver/ carbon rod/ none
carbon rod/ silicon (synthetic)/ good
carbon rod/ zincite (Poland, synthetic)/ good
chalcocite/ zincite (Poland, synthetic)/ very good
chalcocite/ silicon (synthetic)/ very good
chalcocite/ chalcocite/ none
chalcocite/ molybdenite/ none
chalcocite/ bronze guitar wire/ none
covellite/ silicon (synthetic)/ fair
covellite/ zincite (Poland, synthetic)/ fair
galena/ zincite (Poland, synthetic)/ good
galena/ silicon (synthetic)/ very good
galena/ bronze guitar wire/ none
galena/ carbon rod/ none
silicon (synthetic)/ jumper wire/ fair
silicon (synthetic)/ copper plate/ poor
zincite (synthetic)/ silicon (synthetic)/ none
zincite (synthetic)/ jumper wire/ poor
zincite (synthetic)/ copper plate/ poor
A Hudson Institute Career Day Sparks “Mineral Diode” Study
By Tony Nikischer & Robert Fung
Excalibur Mineral Corporation
One of us (TN) recently presented the Hudson Institute’s annual “Career Day” mineral seminar at a local middle school, bringing minerals, meteorites, UV lamps, periodic tables and assorted household items to demonstrate the use (and beauty!) of minerals common in our everyday lives. “Career Days” give kids the opportunity to learn about the work that adults perform in a wide variety of professions, hopefully providing some insight into what interesting jobs and educational paths are open to today’s youngsters. It is a yearly ritual that is well received by the students and teachers alike, and in the case of the Hudson Institute’s participation with Excalibur Mineral Corp., many free mineral specimens are distributed to the students who attend the “geology” lectures. Energizing the next generation of collectors and mineral scientists is also a primary aim of our joint participation!
Not surprisingly, many youngsters were amazed at “how cool” the study of minerals could be, and their use in electronic devices created some special interest among this avid cell-phone, video game-playing crowd. It was an eye-opening experience this year, particularly because the kids were very technologically adept, but few had a real understanding of how their various electronic devices actually worked. (Welcome to my world!) While I can recollect my older brother being one of the first kids on the block to build his own “crystal radio” back in the 1950s, the electronics bugs never really bit me, and I felt woefully inadequate in explaining specific “mineral phenomena” with regard to everyday electronic gizmos. My number one, electronically-literate, Excalibur associate, Robert Fung, came to the rescue! Taking a common electronic device, the diode, and looking backwards at its mineralogical history, provided some useful information for a future “Career Day” presentation.
In the mid-1800s, scientists began experimenting with wireless signaling, an outgrowth of earlier observations and theories of electromagnetism that were being developed at the time. It was a period of explosive discovery, with names like Ampere, Faraday, Hertz, Tesla, and Rutherford all working their magic. And minerals were in the middle of it all, as radio’s origins began as “wireless telegraphy” that utilized minerals and mineral synthetics. It was Karl Ferdinand Braun who, in 1874, discovered and described the galena rectifier in his treatise Ueber die Stromleitung durch Schwefelmetalle (On the Flow of Current through Metallic Sulfides) from which the first diodes emerged. Twenty years later, Sir Jagadish Chandra Bose (Bengal) used a "cat's whisker" diode to detect radio waves, subsequently patenting the galena detector (an early radio diode) in 1901.
Although this is not a lesson in electronics, it is useful to know what a diode is and what it does, and why its discovery and use, based on conductive properties of certain minerals, became so important. In an admittedly over-simplified nutshell, a diode is a device that allows current to flow in only one direction, much like the way a gate valve in a liquid-based system works. As the simplest form of semi-conductor, diodes can act as rectifiers that convert AC to DC, and they can also demodulate the amplitude of electromagnetic waves. Many specialized diodes were developed, enabling the devices to detect and tune radio and TV signals, act as photovoltaic cells in solar energy systems, or emit visible light or infrared energy as in LED’s. Their evolution from early mineral bits to vacuum tubes to development of the transistor had a huge impact in the expansion and production of what are now everyday electronic devices.
In 1922, H.S. Roberts and L.H. Adams published an abbreviated list of mineral semi-conductors (American Mineralogist, Vol. 7, No. 8, pgs 131-136) based on their experimental observations of common “crystal detectors” made of various minerals. Of the thirteen (13) species they included, most had simple chemistry (10 of 13 had two elements, the remaining ones with only 3 elements), high symmetry (10 were isometric or hexagonal), and cleavage seemed to play no significant role. Three years later, Edgar Wherry (of wherryite fame) tested a large number of additional minerals, utilizing a copper “cat’s whisker” and a simple crystal set, finding some 75 species with radio detector properties (see American Mineralogist, Vol. 110, No. 1, pgs 28-29).
Because Wherry’s interesting experiments utilized many different species, one of us (RF) decided to attempt to duplicate the results of his “cat whisker” findings, using both a modern day oscilloscope as well as a primitive crystal radio. We selected several specimens from the Excalibur inventory (see figure 1) and prepared the first of two different experiments. In each case, a small sample, approximately 1 cm3, was trimmed from a larger specimen. A 1.2 diameter brass tube was cut into small 1cm tall sections, and was then placed on a copper circuit board. Bismuth (extracted from shotgun pellets) was heated to molten state in a crucible and then poured into the brass tube holders. While still liquid, the mineral fragment was then dropped into the bismuth-filled “vat”, and the resulting “ohmic electrode” was allowed to cool.
Figure 1, below: Table of minerals for first experiment
Bornite + Ankerite: Baltic Mine, Newton, Michigan
Bornite + Silver: Magma Mine, Superior, Arizona
Bornite + Chalcocite: Mt Con Mine, Butte, Silver Bow, Montana
Chalcocite: Unknown Locality, ex. A.E.Seaman Museum
Covellite: Butte, Montana
Galena: Ravilli County, Montana
Molybdenite: San Manuel Mine, Arizona
Molydenite: Ashdown Mine, Humboldt County, Nevada
Tennantite: Trixie Mine, Utah
Tetrahedrite: Casapalca, Peru
Zincite w/Franklinite: Franklin, New Jersey
The brass winding from an electric guitar string was used as a cat’s whisker, and it was connected to one input of our oscilloscope setup, while the other input was connected to a wire soldered to the diode base. If good contact was made, we were able to observe an asymmetrical wave deflection on the oscilloscope, and the steepness of the deflection was deemed as either poor (for low or no deflection) to fair, good or very good (for very steep deflection angle). Our results closely matched those of Wherry’s 1925 diode experiments.
In a second set of experiments, we selected additional samples and prepared “p-n junction” diodes utilizing two different minerals, connecting them to an audio amplifier, and attempting to pick up our local Peekskill radio station. We achieved a wide range of results, depending on the combinations of minerals or materials used in our diodes (see figure 2). Not surprisingly, combinations that used good conductors such as galena and chalcocite, in conjunction with synthetic quartz or synthetic zincite (from those Poland paint factory chimney specimens of some years ago), produced the best results.
So, if you are bored with collecting fancy, crystallized minerals, or you are just looking for something off the beaten path to do with your excess mineral specimens, try some of these kooky experiments. For those of you who are Ham radio operators, or for others who get radio station reception from the fillings in your teeth, yes, we have more work to do! One of us (RF) is now building a basic tuner, so that we can search for a wide range of frequencies when running experiment #2 again. And just to be complete, we’ll check tooth filling materials (silver-amalgam [Ag,Hg] and others) against hydroyxlapatite, just to confirm that the voices you hear in your head are not a result of being nuts, like we are……
Figure 2, below: Additional mineral combinations were constructed and used as p-n junction diodes. The subjective results of our local radio reception is noted in the third column.
Mineral contact #1 / Mineral contact #2 / Radio Signal
bismuth / zincite (synthetic)/ fair
Bornite + Chalcocite/ zincite (Poland, synthetic)/ good
Bornite + Chalcocite/ silicon (synthetic)/ good
bornite + silver/ molybdenite/ poor?
bornite + silver/ zincite (Poland, synthetic)/ good
bornite + silver/ silicon (synthetic)/ good
bornite + silver/ zincite(nj)/ none
bornite + silver/ chalcocite/ none
bornite + silver/ covellite / none
bornite + silver/ enargite/ none
bornite + silver/ carbon rod/ none
bornite + silver/ bronze guitar wire/ none
bornite + silver/ jumper wire/ none
bornite + silver/ galena/ none
bornite + silver/ carbon rod/ none
carbon rod/ silicon (synthetic)/ good
carbon rod/ zincite (Poland, synthetic)/ good
chalcocite/ zincite (Poland, synthetic)/ very good
chalcocite/ silicon (synthetic)/ very good
chalcocite/ chalcocite/ none
chalcocite/ molybdenite/ none
chalcocite/ bronze guitar wire/ none
covellite/ silicon (synthetic)/ fair
covellite/ zincite (Poland, synthetic)/ fair
galena/ zincite (Poland, synthetic)/ good
galena/ silicon (synthetic)/ very good
galena/ bronze guitar wire/ none
galena/ carbon rod/ none
silicon (synthetic)/ jumper wire/ fair
silicon (synthetic)/ copper plate/ poor
zincite (synthetic)/ silicon (synthetic)/ none
zincite (synthetic)/ jumper wire/ poor
zincite (synthetic)/ copper plate/ poor
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