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“It may not be generally known that an ordinary horseshoe magnet when drawn over a piece of magnetite (best over a smooth section) induces considerable magnetic polarity or remanence in the specimen.  The material becomes lodestone.  A powerful electro-magnet is much more efficient.”

John W. Gruner responding to W. H. Newhouse's submission on "The Identity and Genesis of Lodestone Magnetite" (Economic Geology, Vol. 24, 1929)

“Perhaps the majority of the mineralogists of the future will be ‘synthesizers’ able to make from a few simple raw materials ‘pure’ minerals for applied science and industry. Conspicuous recent examples are quartz and diamond.  Does this call for a redefinition of the scope of mineralogy?  If one applied 150,000 bars of pressure to make stishovite, has he become a physicist, or is he still a mineralogist?  If he uses physical or chemical theory to interpret some natural occurrences or their absence should he be called a geophysicist or a geochemist rather than a mineralogist?”

John W. Gruner, upon accepting the highest award of the Mineralogical Society of America (American Mineralogist, Vol. 48, 1963)

Some history

Due to Bruno Doss’ 1906 work on three gas wells on the property of the Mel’nikov brothers in the Samara Province of Russia, between 1912 and 1964 the black iron sulfide mineralogists now know as greigite was known as melnikovite. See The Oxidation and Reduction Potential in Geology, Consultants Bureau, New York (1972) (trans. J. Paul Fitzsimmons) (“O-R”) citing, among other papers, Doss’ Ezhegodnik po Geol. I Mineralogii Rossii, Vol. 12, No. 5-6 (1911).

Henry Lepp apparently was the first person to synthesize melnikovite. Economic Geology, Vol. 52, pp. 528-535 (1957).  Lepp did his melnikovite synthesis and wrote his report on melnikovite’s “probable geological significance” as part of his 1954 University of Minnesota doctoral dissertation under the guidance of Dr. Gruner. Id. at 534.

Based on R. A. Berner’s work, as reported in American Mineralogist, Vol. 49, pp. 543-555 (1964) and in O-R, it was only Lepp's lack of “natural” melnikovite specimens that prevented him from providing "positive proof” of correspondence between natural and synthetic melnikovite. See Economic Geology, Vol. 52 at pp. 528-529.  Note too that O-R’s author, Mikhail F. Stashchuk, was the director of the Laboratory of Mineral Forming Processes of the Institute of Mineral Resources of the Ukranian Ministry of Geology when he publicly stated that before the appearance of the structural investigations of Lepp it was impossible to state reliably what melnikovite was.  O-R, p. 68.

According to the mineralogy website Caltech and the University of Arizona maintain, greigite’s identification has been confirmed “only by single crystal X-ray diffraction.” See http://rruff.info/greigite/display=default/, accessed March 11, 2016.

In B. R. Doe and D. K. Smith's Studies in mineralogy and Precambrian geology: A Volume in Honor of John W. Gruner [The Geological Society of America, Memoir 135] (1972) (“Studies”), author Bruce Doe states he (too) worked under Dr. Gruner’s tutelage in the early 1950s and a homemade, cold cathode X-ray machine was the diagnostic tool the Roebling Medal winner (Gruner in 1962, see above quote) preferred to an X-ray diffractometer, at least for analyzing sheet structure minerals.  See Doe’s introduction to Studies.

David L. Southwick’s “Memorial to Henry Lepp” does not include Lepp’s PhD thesis in its "selected bibliography" and does not address the tool(s) Lepp used to do mineral analysis, so it may never be known if it was Dr. Gruner's cold cathode X-ray machine that helped Lepp analyze the iron sulfide mineral he synthesized and on which Economic Geology reported in 1957.  See ftp://rock.geosociety.org/pub/Memorials/v22/Lepp-H.pdf, accessed March 11, 2016 and Economic Geology, Vol. 52, infra.  But the machine likely was the tool Dr. Gruner used to analyze his samples of (what W. H. Newhouse called) “lodestone magnetite.” See Economic Geology, Vol. 24, pp. 771-775 at pp. 772-773 (1929).

Dr. Gruner noted his hand-specimen of lodestone showed greater magnetism at the edge than at the center and it is on the surface, at the extremities of magnetite deposits, where lodestone is found. Lepp observed different phases of Fe2O3.H2O when his synthetic "melnikovite" oxidized in water as opposed to room-temperature drying.  See Economic Geology, Vols. 24 and 52, infra.  These observations, and the observation of how use of a firm cavity can counteract the magnetic edge effect and avoid shear, may prove meaningful as research continues on...


Scientific Papers of note (in addition to those cited above)

“A search for bacterial magnetite in the sediments of Eel Marsh, Woods Hole, Massachusetts

This appeared at https://catalog.stanford.edu/view/1030039 (and later at https://searchworks.stanford.edu/view/1030039) as a thesis that (master’s degree candidate) Anne Demitrack submitted to Stanford University’s geology department in 1982. In this thesis Demitrack postulates the existence of a greigite-producing magnetotactic bacterium, apparently for the first time.  See also http://web.gps.caltech.edu/~jkirschvink/magnetofossil.html (but note here the year 1985, not 1982, is cited by author Kirschvink as the year Ms. Demitrack submitted her Stanford University master’s thesis.) 

American Mineralogist, Vol. 79, pp. 654-667 (1994)

Drs. Jillian Banfield, David Veblen, and Peter Wasilewski report their findings from using U. S. National Museum (“USNM”) “type 1 lodestone” specimen 99484 to “investigate relationships between the microstructures and magnetic properties of strongly magnetized magnetite and maghemite” as revealed by transmission electron microscopy (“TEM”).

Geophysical Research Letters, Vol. 26, No. 15, pp. 2275- 2278 (1999)

Using the same USNM specimen (99484) for their “lightning experiments” at Langmuir Lab, Goddard Space Flight Center scientists Peter Wasilewski and Günther Kletetschka (tacitly) confirm Dr. Gruner’s research findings on how “lodestone magnetite” can get charged simply by magnetic touching. See page 2278.  See also Economic Geology, Vol. 24, infra at 773.

Geophysical Journal International, Vol. 141, pp. 809–819 (2000)

Mark Dekkers et al. report observing magnetite and maghemite upon heating hydrothermally-synthesized greigite to above ~400°C.  (Cf. Economic Geology Vol. 52, supra at 532, regarding Henry Lepp's heating of his synthetic material to only 200°C.)

American Mineralogist, Vol. 91, pp. 1216-1229 (2006)

A team of seven researchers (Japan, UK, Hungary and USA) examine the magnetic properties, microstructure, composition, and morphology of greigite nanocrystals in magnetotactic bacteria from electron holography and tomography with the goal of "obtaining a better understanding of the function of magnetotaxis in sulfide-producing cells...and [assisting] interpretation of the paleomagnetic signals of greigite-bearing sedimentary rocks."

Rev. Geophys., Vol. 49, Issue 1 (2011)

A. P. Roberts et al. provide an “update” on the magnetic properties of sedimentary greigite.

Science, 334:6063, pp. 1720-1723 (2011); https://m.youtube.com/watch?v=LeKx6jrDOos, accessed March 6, 2016

Christopher Lefèvre et al. isolate a greigite-producing magnetotactic bacterium from a brackish spring in Death Valley National Park, California, USA and culture it; Christopher Lefèvre discusses his ongoing work (apparently at IBEB) with greigite-producing DeltaproteobacteriaSee video uploaded by Labex MATISSE MiChem PlasaPar and cf. Microbiological Research, Vol. 167(9), pp. 507-519 (2012).

Geochem. Geophys. Geosyst., 14, 5430-5441 (2013)

A. R. Muxworthy et al. discuss the implications for magnetosome crystals of critical single domain sizes in chains of interacting greigite particles.

J. Mater.Chem.A 2, pp. 1903-1913 (2014)

Ernst Bauer et al. form greigite by vapor-solid reaction and establish 450°C as greigite’s “lower limit” Curie temperature.

Earth-Science Reviews, Vol. 151, pp. 1-47 (2015)

A. P. Roberts discusses magnetic mineral diagenesis

Environmental Microbiology Reports, 8: 1003–1015 (2016)

Christopher Lefèvre et al.'s results show that Desulfovibrio magneticus, a species of dissimilatory sulfate-reducing magnetotactic bacteria, is capable of aerobic growth with O2 as a terminal electron acceptor.

Geomicrobiology Journal, published online 12/29/17, http://www.tandfonline.com/doi/full/10.1080/01490451.2017.1362078

A greigite and cellular content of a magnetotactic bacterium scanning transmission X-ray microscopy study by Canada-based researchers suggests greigite has a different electronic and magnetic structure than magnetite despite having the same crystal structure.


"lodestone from greigite" research made possible by  

and the libraries of Occidental College and Caltech

with special thanks to

-- Gail Clement of Caltech, for her encouraging words and

help accessing O-R and J. Mater.Chem. A 2

-- Dr. Scott Fendorf for helping our daughter in her

Stanford University geology/soil science studies and for

his reference to Cornell and Schwertmann's book

The Iron Oxides, WILEY-VCH (2d ed., 2003).  The graph on

page 160 (Fig. 7.21) showing normalized remanent

magnetization as a function of temperature for maghemite,

greigite, magnetite etc. proved illuminating for many reasons.