Geobotanical Prospecting

File today’s post – which is dedicated to Adam Large, wherever he may be – under “Ideas that seemed a lot more radical when I first speculated about them ten years ago” or else “Time marched on. Did my own thinking about x,y,z advance with it?”:

Some plants are strongly correlated with deposits of particular minerals (e.g., Ocimum centraliafricanum for copper or juniper/sage for Uranium) — whether because the ore body alters the surrounding geochemistry in a way that’s favorable to the plant, or because the plant can absorb large quantities of the mineral without toxification, or some other reason. The investigation of such indicator species for purposes of identifying new mineral deposits is called geobotanical (or just botanical) prospecting.

Every plant has a unique spectral signature which can be detected using near-IR or some other sensor band. In theory, it should be possible to forensically interrogate all space-based and aerial imagery that was captured with the appropriate bands (and perhaps not even with those, as algorithms get better at detecting indirect evidence of one electromagnetic narrative hiding within another) for any purpose historically – not just prospecting – in order to classify spectral signatures of known indicator species amidst background noise (i.e., the rest of the imaged planet) and eventually produce a global “base map” (in the nomenclature of my former employer) of indicator species that could be mashed-up with a variety of other proprietary data, further filtered algorithmically based on industry expertise, and so forth, to help improve the efficiency of prospecting — one of the main cost centers of the mining industry. 

By similar means — insofar as imagery catalogs enable a limited form of time travel — candidate indicator species for certain minerals (e.g., two of the hobbyhorses in my personal stables: gold and rare earths) might be identified where none currently exist.

If one had an archive of historical imagery with the right bands and resolution, you could take the locations of known gold, platinum, silver, and REE deposits, wind the clock backward to look for imagery prior to their exploitation (i.e., before the vegetative ground cover got destroyed) and back out the spectral signatures of plants surrounding the deposits. By excluding all of the known signatures associated with deposits of a particular mineralogical type, it should be possible to identify candidates of new species to feed into an analysis pipeline identical to the one described above.

Such archives are spotty, of course, and in any case probably only extend back 25-odd years. Other sources may exist that could help fill in the patchwork gaps between the first overflown multispectral imagery and the present, but it’s fair to say that the global vegetation imagery record — like the archaeological record, the fossil record, the art history record, or any other historical data set — will remain incomplete, and that “before” images for only comparatively recent mining operations will be analyzable. Even so, as I explained to the founder and chief brainiac of the then-largest commercial satellite company in the world back in 2014, it doesn’t hurt to try. For all I know, they did.

Here are a few of the indicator species I collected information about in the immediate wake of my divorce a decade ago. It was nice to have flowers around the house. Especially those that blabbed silently, electromagnetically, about buried treasures.

Astragalus bisulcatus (aka Two-Grooved Milkvetch), an indicator species for vanadium deposits in uraniferous sandstone in the SW United States.

Mielichhoferia elongata (aka Elongate Copper Moss) is a cuprophilous bryophyte endemic to the Alps, Auvergne, the Pyrenees, and the mountains of Swedish Lapland and Norway. For some reason, it can also be found near Corrie Kander, Aberdeenshire and Ingleby Greenhow, Cleveland.

Digitalis purpurea (aka Foxglove, Witch’s Glove, Dead Men’s Bells, Fairy’s Glove, Gloves of Our Lady, Bloody Fingers, Virgin’s Glove, Fairy Caps, Folk’s Glove, Fairy Thimbles, Lion’s Mouth, Fairy Fingers, King Elwand, Foxbell, Floppy dock, Flowster-Docker, Fingerhut, Revbielde, &c.), a local indicator species for iron deposits in Russia and manganese deposits elsewhere in Europe.

Convolvulus althaeoides, an indicator species for phosphates in the Mediterranean Basin. Believed by miners in Estremadura, Spain, to be “a most reliable guide to the scattered and hidden deposits of phosphorite occurring along the contact of the Silurian slates and Devonian dolomite.”

Hyptis suaveolens, an indicator species for copper deposits in the Malanjkhand granitoid of Madhya Pradesh, India. Copper from the overlying soil accumulates in certain of the plant’s organs and stunts its growth characteristically.

Persicaria hydropiper (aka Smartweed or Water Pepper), an indicator species for hematite deposits in China. First identified as such by Zhang Hua — a Jin dynasty poet and military advisor to the Emperor Wu. Hua was killed in 300 BCE after the Empress Jia (who had herself seized power from Wu’s grandson in a coup d’état) was executed in a coup.

Crotalaria cobalticola, a rattlepod endemic to the Katangan Copperbelt region of the DRC, is an indicator species of cobalt deposits in the copper-rich soils there.

Alyssum bertolinii (aka Madwort), a nickel hyperaccumulator endemic to ultramafic soils. Indicator species for nickel deposits in Italy and elsewhere in Europe.

Astragalus pattersonii (aka Patterson’s Milkvetch), an indicator species for sandstone-type uranium deposits in the western United States. It thrives on the direct intake of selenium from ore bodies located at depths of up to 23 meters.

Viola calaminaria (aka Yellow Calamine Violet), a zinc hyperaccumulator. Indicator species for zinc deposits in Europe.

Eriogonum ovalifolium (aka Cushion Buckwheat), an indicator species for silver deposits in the western United States.

Equisetum Arvense (aka Horsetail), the last surviving genus of Equisetopsida. It is an indicator species for gold deposits in the Pacific Northwest, Alaska, and Southern Arctic.

Ocimum centraliafricanum (née Becium homblei), an indicator species for copper deposits in Central Africa.

Needless to say, there were others.

2 Responses to “Geobotanical Prospecting”

  1. priezza Says:

    Well-written.

  2. Bough wow wow yippie yo yippie yay | Chamblissian Says:

    […] two longstanding interests of mine – in geobotanical prospecting and the mythopoetics of the Campi Flegraean volcanic province – I want to bioengineer a […]

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