How can I use horsetail as a "indicator plant" to find gold while gold pannig?

Question

How can I use horsetail as a indicator plant to find gold while gold pannig?

What are Indicator Plants?

Indicator plants are peculiar to a certain place. Though they aren’t necessarily rare, they don’t grow just anywhere. They tolerate only a narrow range of growing conditions, so their presence in a forest signals some distinctive aspect of that place.

Indicator plants can be used for a variety of reasons. They can tell us if we are the wetlands, an old field, a young woodlands, mature woodlands, human impacted sites or whether the soil is alkaline or acid and so on, as seen here and here.

Field horsetail indicates a wet, poorly draining soil and is soggy at different times of the year as is mentioned here.

Horsetail is a perennial plant that is found in or near watery areas such as marshes, streams, or rivers. Horsetail grows in temperate northern hemisphere areas of Asia, Europe, North America, and North Africa. It flourishes where it can root in water or clay soil.

There are some who claim that horsetail can be used as an indicator plant for finding gold, such as the following:

Some of the most useful plants for mineral prospecting are:

• Gold - Equisetum arvense & confusa (horsetail) - Indicator Plants

The following site has this to say about horsetail:

The horsetail is a type of plant that grows in sandy soil usually very close to a water supply. Its uses are many as it has a high silica content that allegedly can be of some medicinal value, but its primary function during the gold rush days was for... - Horsetail Gold

My question is this: How can one know the differences between what makes a site possibly gold bearing over one that in simply wet, poorly drained and/or sandy, using horsetail as a plant indicator, while gold panning along a river or stream in the Great Outdoors?

Answer 1

You can't.

The theory required you to get samples and send them to a lab, which wouldn't exactly be practical in the field anyway.

METAL ABSORPTION BY EQUISETUM (HORSETAIL)

A19 GOLD AND SILVER

Gold in Equisetum throughout the conterminous United States ranged from less than 0.1 ppm in the ash to 0.4; the latter amount was in a sample collected as background material from Utley, Henderson County, Ky. Of the samples from mineralized areas, those collected in gold-producing districts averaged 0.17 ppm compared with 0.12 ppm in non-gold-producing areas. The samples collected in Alaska averaged 0.34 ppm; this value corresponds closely with those obtained by War- ren and Delavault (1950) for Canadian samples. The difference in average content in plants growing on mineralized and unmineralized ground however, is not significant and suggests that Equisetum would not be useful in prospecting for gold. Silver is absorbed by Equisetum more readily than gold, and the amount of silver absorbed seems to be related to the amount of silver present in the soil. Samples collected at the silver-producing Ore Hill mine, New Hampshire, averaged 1.4 ppm; those from other mineral districts averaged 0.7 ppm.

Answer 2

That doesn't necessarily mean that Equisetum arvense is a poor indicator of gold. It simply means that the plant does not take up enough gold in mineral rich areas to be significant (gold is a noble metal and as such it doesn't "like" to be ionic and I thing most plants use an ions charge in conjunction with water to pull the metals in..) but it may well grow in areas whose geologic characteristics that tend corresponds to gold deposits. Then again it may not.

It is my understanding that gold accumulates in loose soils but stops at bedrock. It is my understanding that equisetum (horse tail) likes to grow in poor draining soils. Poor draining soils = loose soils near bedrock? Mind you that while I have a degree in chemistry and training in chemical engineering this is not my field of expertise. Good luck and have fun.

Here is a link to an old report from the USGS...

Gold in Plants

Answer 3

The gold you find while panning didn't originate locally. It came from a gold vein in a rock somewhere but was eroded to tiny particles, carried off with a water current and deposited somewhere where the current becomes weaker. If you see horsetail growing you've found an area where there is water and probably not too much current in any part of the year. It does not tell you if there are or were gold deposits upstream, it does not tell you how much or little current there is higher upstream and it does not tell you how long the situation has been like this. It's an indicator of one prerequisite for finding gold. You can use it when you learn indicators for other factors involved as well.