What type of rock is best?
Feeding poor soil with mixed rock dust may be compared
to feeding an ill person a varied diet of unrefined,
natural food. If no one single food is a panacea, it might
follow that no single rock type is "ideal." Indeed, the
virtue of glacial gravel is said to lie in its broad
spectrum of rock types. The late John Hamaker advocated
the use of glacial gravel dust, ideally followed by river
and seashore gravels and mixtures of single rock types.
In the book The Survival of Civilization, John
Hamaker suggests finely-ground glacial gravel because that
is nature's way throughout millennia to create fertile
soils. Glacial gravel, which is a natural mixture of
rocks, will create a broad spectrum of minerals in the
soil in a natural balance.
Much of value can also be gleaned from Europe and the
research and experiences there where single rock types and
combinations of single rock types such as basalt are used.
Hamaker asserts that "Micro-organisms select what they
need to make the compounds of life, and reject to the
subsoil what is not needed, [such as] aluminum, silicon,
iron, etc., which are generally in excess [in gravel
dust]," further pointing to "the Kervran research on
biological transmutations", which suggests that biological
organisms may play an active role not only in selecting
specific elements, but also in modulating their elemental
nature to create needed materials where they are in short
supply. Hamaker says "As long as the soil is neutral [in
pH] or close to it, microorganisms will control what goes
into the plant roots. These controls are off when the soil
is acid or acidic chemicals are added."
Composting with rock dust
Combining gravel dust with organic materials in compost
is a great way to solve application problems and speed up
the process. Don't forget a handful of soil to inoculate
with organisms. Gravel dust improves aeration and
structure and therefore prevents rotting. Gravel dust is
assimilated even more quickly in compost than in poor
Compost and gravel dust are a symbiotic combination:
the compost provides an excellent medium for the
"microorganism population explosion" promoted by the dust,
and the gravel dust will not only help create more organic
matter, but will also help hold it in place, reduce odors
and conserve it.
Add 2-20 lb. of rock dust per cubic yard of compost, if
one is doing pile or window composting.
Soil pH should be measured annually. If the soil is
acidic, agricultural limestone may be added together with
the rock dust to bring the soil pH to neutral. Gravel dust
will also neutralize soils to a great degree, but
limestone is a quick remedy for agricultural soils.
Limestone is not recommended for forests as it will
destroy the humus-building complex in the long term.
Keep insects in natural balance in your garden
For short-term rescue, very fine dust sprayed directly
on plants and trees has been shown in research in Germany
to deter insect infestations very effectively. Trails of
rock dust around the garden help keep slugs out. And
healthy remineralized plants will not be plagued by insect
infestations in the future as they become healthier and
more insect resistant.
How to apply gravel dust
There are many ways to apply dust to the soil; which
method you use depends on the scale and your preference.
It can be spread by hand out of a wheelbarrow using a
shovel, or roto-tilled and disked in. You can use a wet
agricultural lime spreader. If equipment is available that
contains an agitator (to maintain particles in a suspended
state), a wet spray can be used.
Organic farmer John Sundquist in Oregon applies it with
a manure spreader, bander or an "E-Z Flow" type fertilizer
applicator. He also uses rock dust in a potting soil made
of compost, ashes and peat moss.
How much to use
A grower of crops or a gardener needs a good response
the first year after a fall application. The response in
any one year depends on the amount of minerals available
to the microorganisms, soil moisture and the amount of
inert organic matter.
If the last two factors are satisfactory, as little as
3 tons of gravel dust per acre worked into the top 4
inches of soil should give good results. However, I prefer
about 10 tons per acre worked in about 8 inches, since one
application will eliminate the cost of a number of more
frequent applications and give high yields.
Application Conversion Chart will help you to
determine how much gravel dust to use: 3 tons/acre is
considered the minimum application, 10 tons/acre is
Hamaker's preferred long-term application, and 20
tons/acre is given as a major remedial application for
especially dry, poor soil. Smaller amounts are recommended
if the rock dust is finer than 200 mesh and larger amounts
if much less fine than 200 mesh.
Finding local sources of gravel dust
To find gravel-grinding operations in your area, call
your local gravel pit (look in the Yellow Pages under
"Cement-Wholesale", or "Sand and Gravel") and ask if they
have crushed gravel screenings made from mixed rocks, the
kind that comes out of river beds - crushed and passed
through a 1/4 inch or finer screen. The gravel dust will
probably cost from $1-$8.00 per ton plus the cost of
transportation if the gravel pit delivers it to your
garden. As most of the cost is in transporting the rock
dust, having a truck or access to one is an advantage. A
cooperative initiative with friends and neighbors would
also cut costs down.
The Particle Conversion Chart shows various categories
of "soil separates" (ground particles) listed with their
diameters in microns (thousandths of a mm.) and their
corresponding screen mesh sizes. "Mesh" simply refers to a
screen with a given number of holes per inch.
The more finely ground the rock, the more readily
microorganisms will have access to the minerals. John
Hamaker uses the term "gravel dust" to mean a dust "90% of
which will pass through a 200-mesh screen."
You can also contact your local state Aggregate
Producers Association, your local county DPW (Department
of Public Works), your state DOT (Department of
Transportation) Materials Bureau and you can contact the
National Aggregate Association (Tel: 1-800-622-1020).
What does industry call the product?
It is referred to as pond settlings, rock dust, rock
flour, classifier tailings, and minus #200 mesh. You
should ask for minus #200 Mesh (-75 micron) material, pond
settling, material that has gone over the weirs of a sand
screw or the weir of a sand classification tank, or
material obtained from the dust collection system. You
should not use concrete sand, abrasive sand, filter sand,
mason sand, blow sand (loess) screenings as they are too
What is the best material to use?
Glacial sand and gravel that contain a myriad or
heterogeneous combination of various rock formation type
or mineralogy is preferred.
Other metamorphic or igneous stone such as basalt,
rhyolites, etc., are highly recommended. Most sedimentary
rocks (limestone and dolomite) are used to balance pH and
provide for calcium and magnesium deficiencies.
Testing your gravel dust
Several people have reported that gravel dust does not
work or it will have [only] a temporary effect. They don't
describe the dust in detail, but there may be very little
dust in what they call 'dust.' Know what you are buying or
you may be badly disappointed.
Here are three simple, quick tests you can perform at
POT TEST: A pot test will give
you immediate, practical proof of what the product will do
in the soil. It is a good idea to add the gravel dust to
clay pots and plant radishes or other fast growing plants
and observe their progress. As John Hamaker writes: "Doing
a pot test is the most convincing argument I know of.
Anybody can do it. There are testing laboratory grinders
everywhere. There is no lag time. In 6 hours you can get a
microorganism population explosion. Taking some 6" clay
pots, I filled them with a 50-50 mixture of earth and peat
and 3 heaped tablespoons of dust. The results were
You can compare different mixtures or samples of gravel
dust depending on what's available in your area. Use a
control without rock dust to compare as well. You can also
begin with small plots in the garden. You can see the
results of the gravel dust you've chosen and then add it
in larger quantities to your garden. Work the gravel dust
into the topsoil, if possible.
SEPARATE LAYER TEST: Purchasing
a product based on its stated screen mesh alone still
leaves room for error. A purchase of 90%, or even 100%, of
minus #200 mesh screenings could contain only sand and
silt, and no true dust. This test will tell you
approximately how much of your "dust" is really dust and
will be suspended in water.
Fill a clear glass half full with your sample and cover
it with about two inches of water. Shake it up vigorously,
then allow it to settle overnight. The dust, silt and sand
will settle into three distinct layers with the dust at
If the container is allowed to stand until the water
has dried out, the dust [topmost] layer will shrink to
about 1/3 the original measurement and give a more
accurate percentage of the dust. Your first observation,
however, will tell you if you are buying mostly sand. The
coarser the grind, the less effective it will be in the
soil, and the more you will need to use per acre.
MOISTURE TEST: If the material
is bought by the yard, there is a probable increase in
bulk when wet. The buyer needs to test so one can know the
actual weight of dust one is applying to the land. Take a
sample, weigh it, then dry it thoroughly in the oven [and
re-weigh it]. This will tell you how much of the weight
you are buying is moisture.
In some, but not all, situations, having a formal
chemical analysis may not be necessary. A pot test and
small-scale trials with fast-growing plants will give you
more accurate information and with less expense. In cases
where you have doubt about its source, you may wish to
have a gravel dust analyzed to ensure that it is free of
radioactive elements and toxic industrial by-products. In
most cases your source will have already had to undergo
such testing in order to get a license to operate. This is
worth some homework. If you are not able to obtain
documentation to your satisfaction, it might be wise to go
ahead and obtain your own independent lab tests. Good
testing labs are listed in Sources and Resources.
More tips from Hamaker
"One other thing might be useful. I put about 2 inches
of sand on our garden before plowing. It will last a long
time and give some yield after the dust is used up. I am
sure it has been contributing to what we grow. Unscreened
sand (preferably fine sand) from a local gravel pit is
much more economical than shipping dust which is mostly
silt and fine sand.
Sometimes the gravel pits have mesh screens and can
measure the exact fineness of the gravel. Though it may be
hard to find the ideal fineness - 90% passing through a
minus #200-mesh screen - it may be practical to use even
if only 20% or so passes through a minus #200-mesh screen
and at least 50% passes through a #100-mesh screen. You
will have the finer material immediately available to the
soil and the rest will break down over time. If most of it
passes through a minus #200-mesh screen, it will have a
fine consistency like flour or cement. The gravel pit may
have machinery to crush the rock finer and may crush it
Soil erosion is an effect of the shortage of minerals
available to support the soil organisms. As Hamaker says,
"That shortage can be made up on any piece of land in the
time it takes to work ground gravel dust into the topsoil.
When that is done, the soil microorganisms begin to
multiply and it is they who prevent soil erosion by
granulating the soil and holding it against both wind and
For a more thorough understanding of SR, read The
Survival of Civilization and order the
Research Packets available through RE, Inc.
Soil Remineralization in Context
Soil Remineralization (SR) creates fertile soils
by returning the minerals to the soil much the same
way the Earth does: during an Ice Age, glaciers
crush rock onto the Earth's soil mantle, winds blow
the dust in the form of loess all over the globe.
Volcanoes erupt spewing forth minerals from deep
within the Earth, and minerals are contained in
Within silicate rocks are a broad spectrum of up
to 100 minerals and trace elements necessary for the
well being of all life and the creation of fertile
soils. Glacial moraine or mixtures of single rock
types applied to soils create a sustainable and
superior alternative to the use of ultimately
harmful chemical fertilizers, pesticides and
SR has been shown in scientific studies to
increase yields as much as two to four times for
agriculture and forestry (wood volume), and to have
immediate results and long term effects with a
Hundreds of thousands of tons of appropriate rock
dust for soil and forest regeneration are stockpiled
by the gravel and stone industry.
A Brief History
Remineralization has mainly been researched and
explored by three distinct groups:
- First, German nutritional biochemist, Julius
Hensel, pioneered SR in the 1880s with his book
Bread from Stones and a modest agricultural
movement came into being. Following his
contribution, many scientists have done research
on SR since the late 1930s in Germany and Central
Europe for agriculture and forests.
More recent researchers include Peter von
Fragstein at the University of Kessel, Germany,
who has researched remineralization as a
slow-release fertilizer with many different rock
types and to deter insects.
The technology was not available at the turn of
the century to produce finely ground rock dust, so
SR, as promoted by Hensel, could not be produced
feasibly on a large scale. SR was revived about
thirty years ago in Europe. Many rock dust
products for agriculture, forestry and sewage
sludge treatment have been created in Germany,
Austria and Switzerland in the last few decades
and have been successfully marketed by the natural
stone industry. Companies such as Lava-Union
(Germany), Sanvita (Austria) and Bernasconi
(formerly known as Zimmerli, Switzerland), along
with many others and the Natural Stone Industry
(Die Naturstein Industrie) based in Bonn, Germany
have also done a great deal of research.
- Second, is the more recently developed field
of agrogeology. This research has been carried out
mainly in Canada, Brazil, Tanzania, the Canary
Islands, and West Africa--especially on laterite
soils. Because of the intense tropical rainfall,
NPK fertilizers are washed out in only a few weeks
and cannot be stored by the soils, and are
especially harmful to the groundwater. Rock
fertilizers not only give nutrients over longer
periods to cultivated plants, but also improve the
ion-exchange-capacity of soils by forming new clay
minerals during the weathering of the fertilizer.
Researchers include William Fyfe and Ward
Chesworth, among others.
- Third, the grass roots movement concerned with
the premise of John Hamaker in the book The
Survival of Civilization, co-authored with Don
Weaver, asserts that SR is not only the key to
restoring soils and forests, but in the larger
context, absolutely necessary and urgent to reduce
levels of carbon dioxide in the atmosphere and
stabilize the climate. Especially recommended are
rock gravels and glacial moraine from glacial
deposits which provide the most natural mixtures
of rocks with the broadest possible spectrum of
minerals and trace elements.
This movement began with Hamaker's writing in
the early 1970s and expanded in the 1980s into a
global grassroots community consisting of
ecologically concerned individuals and
organizations, farmers and gardeners, scientists
and policy makers.
To facilitate networking and the flow of
information and promote SR as advocated by John
Hamaker and Don Weaver, Soil Remineralization, A
Network Newsletter, began in 1986 and became the
Remineralize the Earth magazine in 1991. The
magazine has networked to people all over the world,
collected research and a wealth of anecdotal results
of farmers and gardeners to substantiate the results
of SR. In October 1995, Remineralize the Earth,
Towards a Sustainable Agriculture, Forestry and
Climate, was incorporated as a non-profit
On May 24, 1994, the U.S. Department of
Agriculture (USDA) (Beltsville, MD), the U.S. Bureau
of Mines (USBM) (Washington, DC), the National Stone
Association (NSA) (Washington, DC), and the National
Aggregates Association (NAA) (Silver Spring, MD)
co-sponsored a forum on "Soil Remineralization and
Sustainable Agriculture" at the USDA Agricultural
Research Station in Beltsville, MD.
The Forum brought together the by-product rock
fines generating industry and the proponents of SR
to explore environmentally-sound uses of rock fines
and to identify the state of the science supporting
their use and the gaps in knowledge that need to be
The USDA began a series of demonstration trials
with rock fines (from Georgia, Maryland and New
York) and other industrial by-products. Dr. Ronald
Korcak, research leader of the fruit lab, directed
the trials over a three-year period. They are also
beginning to research the use of rock dust in
compost under the direction of Dr. Larry Sikora. The
now defunct U.S. Bureau of Mines designed a
prototype for a GIS (Geographic Information Systems)
database to target soils in most need of SR and
their distance from regional sources of rock fines
to calculate transport costs and marketability of
specific rock fines. The National Aggregate
Association has a Task Force on Remineralization
exploring the possibilities for creating sustainable
products for agriculture, forestry and other uses.
Research projects are currently underway at
universities and as part of research and development
programs of some of the largest aggregate companies
in the US, Europe and Australia and through
organizations such as Men of the Trees in Australia.
Just a paradigm shift away from conventional
chemical NPK farming is a vast new frontier, SR -
key to the sustainable agriculture of tomorrow. The
agenda for SR is clear. It will create abundance in
an era of diminishing resources and shift us away
from fossil fuels. Remineralization is nature's way
to regenerate soils. We can return the Earth to
earlier interglacial Eden-like conditions through