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goldbrick

Calling For Help With Old Petrology Terminology!

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I am very interested in pocket hunting. There is not a lot of info on the net about this subject but what there is I think I have studied most of it. Where I feel deficient in my pocket hunting education is old petrology terminology. It seems like over the last 100 years there have been many changes in the names of rocks and minerals. Following is an excerpt from the Canadian GPEX gold forum which may help to illustrate the problems which beset the modern prospector when he tries to decipher what the old-timers were saying.

"The chemical or mineral composition of this pocket formation is generally silica, lime, soda, alumina, potash, copper, lead, magnesia, iron, gold, quartz and water, although these conditions differ in each locality.  (Here I note a problem in terminology. The author uses 19th century mineral terms that I have difficulty translating. Calcite was not used in those days, but the term for it he used was lime, so I substituted calcite in places for today's readers. Soda and potash may have referred to sodium and potassium feldspars, but I'm guessing here. Magnesia may have been magnesite, MgCO. I don't know what the contemporary equivalent for alumina is. He interchanged terms for elements with those for minerals, so the particular minerals containing lead, sulfur and copper may have been understood by his contemporaries, but I don't know what he meant. Chloride puzzles me. Chloride had a meaning among mining men in those days that is no longer used and leaves me mystified)"

Hopefully someone with experience in this area will school us prospectors that lack the ability or knowledge to translate the old terminology into a more modern one. I don't believe I am the only prospector who thirsts for this knowledge or could benefit from publication of it.

Thanks,

Merton

 

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6 hours ago, goldbrick said:

I don't know what the contemporary equivalent for alumina is.

I bet Nevada Chris (Ralph) knows all of these and will respond.  In the meantime, I looked up a couple on Wikipedia and have cut and pasted the parts meaningful to your post:

"Aluminum oxide --Al2O3  -- is commonly called alumina.  It occurs naturally in its crystalline polymorphic phase α-Al2O3 as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire."

"Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase."

 

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Merton,

I am sure of the context you are referring to regarding chloride. Could it be a carry over from the "chlorination process" to free gold from sulfide ores yielding a "chloride of gold"?

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Hardpack, I am just as confused as you. That's why I asked for help ;-)

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Merton I thought you did a pretty fair job of summarizing your interpretations. I think the first step is to buy yourself (a) the simplified Petersen field guide to common gems, ores, and other rocks and minerals authored by Frederick H. Pough.

This book is about 1/3rd of an inch thick and is very understandable in learning about basic mineralogy, for example basic rock formations, basic crystal forms, simple field tests to identify minerals, followed by brief sections ranging from native elements, and commonplace... sulfides and sulfosalts, oxides, haloids, carbonates, sulfates, a section on phosphates, vanadates, uranates, arsenates, and a final section on silicates that provides a pretty good breakdown on feldspars including the plagioclase feldspars... chemical formulas, crystal types, where you learn about some of the terms you listed above.

It also covers the quartz, zeolites,amphiboles, pyroxenes, and the garnet groups. All with good illustrative photos. (b) the full Petersen Field Guide entitled Rocks and Minerals by the same author... which covers just about any subject you're likely to ever need in more detail. It is illustrated with decent photos and decently easy to read, I use it as a reference volume and refer to it constantly for information about minerals we are interested in finding in eastern Ontario. These include the more commonplace materials such as quartz, apatite, titanite, tremolite, fluorite, beryl, garnet, corundum, some feldspars such as moonstone, sunstones and amazonite, and so forth. 

Learning about mineralogy seems a bit challenging, but in time, combining reading and field work quickly gives you a pretty fair working knowledge. Hope this helps a bit at least. :smile:

Jim.

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Hello Jim, I took your advice and bought the Petersen Field Guide. Learning mineralogy is challenging but I will keep stumbling along and learn it eventually(I hope). The terminology has changed so much over the years that it makes a difficult subject much harder to decipher when dealing with historical accounts.

Merton

 

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Jim, I found the following at Amazon.  Are these the two?

(I think I reversed the order -- first one is 461 pages and 1.1 in thick; second is 128 pages and 0.3 in thick.)

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That's them - I modified your links and added the pictures to make it clearer which is which.

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Meanings do change over time. Here is a good comprehensive reference from 1920 that can sometimes clear up older definitions or terminology no longer in use:

A GLOSSARY OF THE MINING AND MINERAL INDUSTRY by Albert H. Fay
WASHINGTON GOVERNMENT PRINTING OFFICE 1920

From the above. The second definition for chloride is interesting as per Merton's speculation.

Chloride.
1. A compound of chlorine with another element or radical. A salt of hydrochloriC acid. (Webster)
2. To follow a thin vein or discontinuous ore deposit by irregular workings, intent only on extracting the profitable parts and with no regard for development; usually said of a lessee, sometimes of one who works another's mine without permission. The term is eaid to have originated at Silver Reef in southwestern Utah when the rich silver chloride ores were being worked. The thin seams were followed by lessees with the least possible handling of barren rock, hence the miner became a chlorider, and his operations chloriding. The words were later extended to similar workers and their operations in other fields. (F. L. Hess)

Magnesia.
Magnesium oxide, MgO. A light, earthy, white substance, obtained by heating the hydroxide or carbonate, or by burning magnesium. (Webster)

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GB_Amateur… yes those must be the two books I suggested above, although the covers have changed since my copies were bought several decades ago. My simplified version is 128 pages, and it is my everyday, keep-it-in-my-knapsack companion that I often refer to when on rockhunting trips. More detail can be had from the larger volume back at camp, incidentally my copy is 317 pages so evidently it has been enlarged.

Merton if you’ve read Jules Verne, particularly Mysterious Island, you’ll find the same chemical / mineral terminology usage dating from the late 1800s… sometimes it is difficult to determine just exactly what material he has in mind. So I understand your frustration. My goal is try to retain an understanding of the fundamentals for mineral identification and to learn rock and mineral associations in areas that specifically interest me. Even that is a pretty tall order considering the diversity of minerals in central, eastern Ontario… specifically the renowned Bancroft area where most of the known minerals do occur.

Steve’s ‘chloride’ explanation for the mining of silver chloride is excellent and in line with your post above. Otherwise, the term 'chloride' refers to a chlorine atom that has taken an additional electron from another element such as sodium (for example ionically bonded table salt NaCl) and added it to completely fill its outer electron orbital path to become a stabilized chloride ‘anion’ that now obviously possesses an overall negative charge (Cl-1 ). Of course in silver bearing areas where chlorine is present, the product could very well be cerargyrite… a silver chloride that you referred to above.

Jim. 
 

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