By Dan Oancea - Twitter

 

In 1556, the first comprehensive book on prospecting and mining, Agricola’s De Re Metalica stated that:

 ”... there are trees whose foliage in spring-time has a bluish or leaden tint, the upper branches more especially being tinged with black or with any other unnatural colour, the trunks cleft in two, and the branches black or discoloured... Therefore, in a place where there is a multitude of trees, if a long row of them at an unusual time lose their verdure and become black or discoloured, and frequently fall by the violence of the wind, beneath this spot there is a vein. Likewise along a course where a vein extends, there grows a certain herb or fungus which is absent from the adjacent space, or sometimes even from the neighbourhood of the veins.”

Modern science has created a special discipline to deal with these early observations. Geobotany is defined as the study of plants as related to their geological environment. It studies the spatial distribution of plants and the characteristics of vegetation as related to geology.

The secret of some plants getting to live where others couldn’t adapt lies in the scientifically term of hyper accumulation, which describes the capacity developed by some of them to tolerate and accumulate high concentrations of heavy metals. Studies suggest that the high accumulation of toxic elements in their tissue could be a defensive mechanism against herbivores or pathogens.

An impressive list of plants that live and thrive on heavy metal soils has been compiled by R.R. Brooks in his 1998 book Plants that Hyperaccumulate Heavy Metals.

Ancient wisdom could still be used by modern geologists as an aid in identifying prospective areas for mineral accumulation.

Some of the most useful plants for mineral prospecting are:

- Gold - Equisetum arvense & confusa (horsetail)

- Silver - Eriogonum ovalifolium (the buckwheat family) and Lonicera confusa

- Copper - Eschscholtzia mexicana (Mexican golden poppy) and Hyptis suaveolens

- Zinc - Viola calaminaria and Philadelphus sp.

- Nickel - Alyssum bertolonii; Berkheya coddii and Thlaspi L. (Ni & Zn)

- Cobalt - Crotalaria cobalticola

- Uranium - Astragalus sp. and Aster venusta.

Numerous references regarding indicator plants could be found on the web including the use of remote sensing images of vegetation cover for deciphering the hidden strata and ore deposits. Vegetation and soil maps of northern Canada and Alaska could also be useful for those involved in arctic mineral prospecting.

Keeping an open eye for subtle changes in plant types and characteristics might provide the modern prospector with the same benefits that the old miners reaped for millennia: a new mine.