Got out yesterday with 2 buddies to Franconia, AZ. meteorite hunting. It's been a long time since getting back out there. I didn't miss all the hot rocks, WW2 bullets and trash, digging 2 foot .50 cal bullets, ect. The GPZ handles hot rocks pretty good, but not out there, there are some hotter than a goats ass in a pepper patch. 😁 But overall it was a nice day, and we all beat the skunk. Here are some H Metal Iron meteorites found out there.
Arent meteorites / meteorite hunting with a metal detector still exempt from placer or lode claims? I know there has been some nice meteorites found in the Rye area's. Just be sure to leave the gold right where its at if you detect it on someones claim... :)
I went out for a couple of days to Gold Basin seeking gold. It was not to be so when in Gold Basin you seek out some meteorites. This trip it was difficult. Nothing until the final couple of hours on Saturday night.
All of my previous locations didn't produce this trip so I went to nearby locations. The larger 37g meteorite was found in an area without many dig holes. It is hard to find a location in Gold Basin without any did holes!
After moving on from that location I went to an area where I could see some very old dig holes. They were deep and big and not filled but weathered down. It was time to slow down. I checked around the dig holes and voila ... a hit about 8 inches from a previous dig. Time to scrape and dig and there is a stick to rock on the magnet. (Was it part of the previous dig hole and meteorite?)
Don't leave your hole in Gold Basin. Check it again. When this was done there was still a target. Upon recovery it was a broken off piece of the meteorite that was dug. They fit.
Total meteorite weight is 54g.
I'm going to stretch the topic just a little bit and tell you that you don't always need to use a metal detector to find meteorites!
This meteorite was found with my eyes and a magnet on Coyote Dry Lake. It weighs 13g and is only my second find there.
The metal detector was in the car. We don't normally use them on a dry lake but sometimes you can. We used the GB Pro one time on a dry lake bed in Nevada to test meteor wrongs vs meteor rights. Let's say we only tested targets we saw and didn't swing randomly. Not all lake or meteorite areas are suitable for metal detectors. Holbrook in northern Arizona is an example that comes to mind. If you don't see it then you aren't going to find it. The ground is too mineralized for a detector to work.
By Steve Herschbach
Gold in Meteorites and in the Earth's Crust, U.S.G.S Circular 603 by Robert Sprague Jones, 1968
Original pdf https://pubs.usgs.gov/circ/1968/0603/report.pdf
The reported gold contents of meteorites range from 0.0003 to 8.74 parts per million. Gold is siderophilic, and the greatest amounts in meteorites are in the iron phases. Estimates of the gold content of the earth's crust are in the range of 0.001 to 0.006 parts per million.
This report is one of several that summarize available data on the occurrence of gold. They have been prepared as background material for the Heavy Metals program of the U.S. Geological Survey, an intensified program of search for new sources of heavy metals, including gold. Data on the occurrence of gold in meteorites and tektites are summarized, and recent estimates of the abundance of gold in the earth's crust are compiled.
GOLD IN METEORITES
Table 1 shows reported gold contents of tektites, aerolites, siderolites, and siderites. The table is arranged so that the data on tektites, which have the lowest iron contents, are at the top of the table and the data on siderites, which have the highest iron contents, are at the bottom. The other meteorite groups are intermediate in iron contents except for the siderolites. Gold is most abundant in the siderites and least abundant in the tektites; therefore, meteorites supply good evidence of the siderophilic character of gold. The tektites and the achondrites are relatively low in gold contents and are distinct from the other groups of meteorites in this respect. The gold contents of tektites and achondrites are of the same order of magnitude as those of terrestrial rocks. The other meteorites, on the average, contain appreciably more gold.
Although the iron contents of meteorites are similar in many respects to those of mafic and ultramafic rocks, the meteorites tend to contain much more gold. In chondrites, the gold seems to be almost entirely in the dispersed metallic phase (Vincent and Crocket, 1960), and this is probably true of the other meteorite. The gold content of the metallic phase of the chondrites is about 1.4 ppm (parts per million), which is similar to the gold contents of siderolites, octahedrites, and ataxites (Vincent and Crocket, 1960; Goldberg and others, 1951).
The carbonaceous chondrites are primitive, relatively undifferentiated matter from which the other meteoritic types have evolved (Mason, 1962; Baedecker and Ehmann, 1965). The occurrence of gold in such primitive types may be of special interest. The average gold content for 13 carbonaceous chondrites is 0.16 ppm, an amount greater than that in the average terrestrial rock by a ratio of about 40 to 1.
It has been suggested (Aller, 1961) that the best approximation to the average composition of the earth's mantle or even the entire earth is provided by the composition of the chondrites. They are similar in chemical composition to the ultramafic rocks, and their isotopic constitution for several elements is basically the same as that for the rocks of the mantle.
Baedecker and Ehmann (1965) shew the abundances of gold, iridium, and platinum in four groups of chondrites. In the olivine-bronzite (H group), the olivine-hypersthene ( L group), and the carbonaceous chondrites, the abundance ratio of Pt :Ir :Au is approximately 7-9:2:1; but for the enstatite chondrites, gold is more abundant and the Pt :Ir :Au ratio is 3.5:0.2 :1. The iridium shows a relatively large decrease with respect to gold. These values, however, represent only analysis of the Abee enstatite chondrite made by Baedecker and Ehmann (1965) by neutron-activation methods. Analysis of this same meteorite by Crocket and others (1967), who also used neutron-activation methods, gives a somewhat different relationship. Their ratio for Pt :Ir :Au is 5.9 :1.5:1. The amount of platinum, iridium, and gold reported by Baedecker and Ehmann is 1.3, 0.083, and 0.37 ppm, respectively; Crocket and others reported 1.3, 0.32, and 0.22 ppm, :respectively. The iridium-gold ratio of terrestrial rocks is more like that of tektites than it is like the ratios of the other meteorites (Baedeckler and Ehmann, 1965).
The gold contents of the octahedrites do nott seem to vary with the coarseness of the octahedrites. Cobb (1967) noted that most of his valules for gold in meteorites were in the range of 0.2 to 2.5 ppm. Cobb (1967) and Goldberg, Uchiyama, and Brown ( 1951) analyzed parts (three in all) of the same meteorite, and Cobb obtained lower values. The average values of gold in hexahedrites were also low compared with those of Goldberg, Uchiyama, and Brown (1951). For the same 11 meteorites analyzed by neutron-activation methods by Goldberg, Uchiyama, and Brown (1951) and Fouche and Smales (1966), the average contents were 1.1 ppm gold and 0.9 ppm gold, respectively.
The various types of siderites have differing amounts of gold. Ataxites and octahedrites have an average gold content of ab1ut 1.3 ppm, which is about twice that for hexahedrites (0.64 ppm). The hexahedrites usually have less nickel than either the ataxites or the octahedrites. The Santa Catharina ataxite contained the most nickel ( 38.5 percent) and r.lso the most gold (4.0 ppm), but the Deep Springs ataxite (13.4 percent nickel) contained the least amount of gold (less than 0.1 ppm, but considered as 0.05 ppm for table 1).
Fouche and Smales (1966) analyzed 70 siderites and found gold contents that ranged from 0.055 to 3.61 ppm. The correlation coefficients between gold and rhenium and between gold and chromium were low and negative, giving values of -0.41 and - 0.31, respectively, but the correlation between gold and arsenic was +0.82 and between gold and palladium +0.68.
Goldschmidt and Peters (1932) analyzed the Coahuila, Mexico, meteorite and reported that it contained 1 to 5 ppm gold, whereas analysis by the neutron-activation method by Goldberg, Uchiyama, and Brown (1951) gave 0.743 ppm gold; by Fouche and Smales (1966), 0.70 ppm gold; and by Cobb (1967), 0.43 ppm gold. Goldschmidt and Peters (1932), analyzed the Mount Joy, Pa., meteorite and reported that it contained 5 to 10 ppm gold, whereas analysis by the neutron-activation method by Goldberg, Uchiyama, and Brown (1951) gave 0.994 ppm gold. These comparative values along with others in this report seem to indicate that lower values are obtained for gold when neutron-activation methods are used.
ESTIMATES OF GOLD IN THE EARTH'S CRUST
Parker (1967) has pointed out the difficulty in estimating the composition of the earth's crust, which forms less than 1 percent of the earth's mass (Aller, 1961). Differences among the estimates given by various authors since Clarke and Washington (1924) are due partly to different concepts of what constitutes the earth's crust, the depth to the Mohorovicic discontinuity, the composition of the oceanic crust compared with the continental crust, and the changes in crustal composition with depth. Also, with respect to gold specifically, the newer method of analysis, that of neutron activation, has resulted in a general downward revision of gold values.
Table 2 gives the various estimates for the abundance of the precious metals, gold, platinum, and silver, in the earth's crust. Precious metal contents of various parts of the earth's crust has been noted by Tung and Chi-Lung ( 1966). These data are given in table 3.
The estimates of gold and silver in the earth's crust have varied little since those of Clarke and Washington in 1924, although the estimates for platinum have varied substantially. The Ag :Pt :Au ratios, based on Tung and Chi-Lung's (1966) figures, are 21 :13:1.
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