Basalt meal, zeolite, lime, dolomite, vermiculite and leonardite – which minerals can really support garden soil.
Anyone who takes a closer look at garden soil will sooner or later come across various mineral soil improvers. Basalt meal, lime, dolomite, zeolite, vermiculite or leonardite – many of these names appear in gardening guides, forums or in conversations with experienced gardeners.
What are rock flours in the garden?
Rock flours are finely ground natural rocks that are used in the garden to supply soils with minerals or to improve certain soil properties. Depending on the type of rock, they can provide trace elements, regulate the pH value or support water and nutrient storage in the soil.
For many hobby gardeners, this is initially confusing. After all, all these materials seem to fulfill similar tasks at first glance: they are supposed to improve the soil. The confusion is sometimes also caused by the fact that they are all called rock flours or primal rock flours.
But in fact, these mineral substances work in completely different ways and it pays to know their exact names and to be able to choose them consciously. Gut feeling is also good, knowledge makes intuitive feeling even more experienced. That's what we think.
So: Some provide minerals.
Others influence the pH of the soil.
Still others improve water and nutrient storage.
Then there are also the paramagnetic properties.
Understanding these differences allows gardeners to support their soil more effectively – creating an important foundation for strong plants and healthy harvests. And a good sense of self-efficacy too.
Why mineral substances are used in the garden at all
A garden soil consists of much more than just earth. It is a complex system of:
- mineral components
- organic matter
- water
- air
- microorganisms
These components work together constantly. Plants absorb nutrients, microorganisms break down organic matter, water moves minerals in the soil.
If this balance is disturbed – for example, by nutrient loss, compaction or extreme weather periods – plant growth can change.
Mineral soil improvers are therefore used to support certain properties of the soil:
- mineral supply
- pH regulation
- soil structure
- water balance
- nutrient storage
Each material fulfills its own function.
The idea behind rock flour – Julius Hensel
The use of rock flours in horticulture has a longer history than many suspect. Already in the 19th century, the German agricultural scientist Julius Hensel intensively studied the role of minerals in the soil. In his well-known work "Bread from Stones", he argued that plants do not only need individual nutrients, but absorb as complete a spectrum of minerals as possible from the soil.
Hensel observed that finely ground rocks can add numerous trace elements to the soil that have been lost over time. His ideas were controversial at the time, but influenced many later approaches in organic horticulture and soil care.
If you are interested in the history of these ideas and their significance for today's soil improvers, you can find a detailed explanation here:
🔗 Bread from Stones – the idea of Julius Hensel and rock flours
Overview of the most important mineral substances in the garden
| Material | Category | Important ingredients | Main effect in the soil |
|---|---|---|---|
| Basalt meal | Soil conditioner | Silicon, iron, magnesium, trace elements | Mineral source, long-term soil improvement |
| Zeolite | Soil conditioner | Silicon, aluminum, various trace elements | Water and nutrient storage |
| Lime | Fertilizer | Calcium carbonate | pH regulation, calcium supply |
| Dolomite | Fertilizer | Calcium, magnesium | pH regulation, magnesium supply |
| Vermiculite | Soil conditioner | Magnesium, iron, silicon | Water storage, loose structure |
| Leonardite | Soil conditioner | Humic acids, fulvic acids | Soil life, nutrient buffer |
| Mineral earth / clay minerals | Soil conditioner | Silicates, clay minerals | Nutrient binding, soil structure |
Basalt meal – great mineral source
Basalt meal is one of the classic rock flours in horticulture. It is produced by the very fine grinding of basalt rock, a volcanic rock rich in various minerals.
Basalt contains, among other things:
- Iron
- Magnesium
- Calcium
- Potassium
- Silicon
- various trace elements
Since these minerals are bound in the rock, they are only slowly released into the soil. Basalt meal therefore does not act like a quick fertilizer, but rather as a long-term source of minerals and trace elements for the soil.
Many gardeners regularly sprinkle basalt meal on beds or add it to compost. There it can help to introduce minerals into the nutrient cycle of the soil.
Paramagnetic properties of basalt
A particularly interesting aspect of basalt rock is its paramagnetic property.
Paramagnetism describes a physical property of certain minerals: they react weakly to natural magnetic fields. Basalt contains various mineral components – including iron compounds – which can exhibit this property.
Some soil researchers and agricultural scientists have therefore investigated whether paramagnetic rocks in the soil could influence certain biological processes.
In this context, it is discussed that paramagnetic materials in the soil could possibly:
- influence microorganisms
- support ion exchange in the soil
- influence electrical processes in the soil environment
These correlations are still being scientifically investigated and are not yet fully understood. Nevertheless, many gardeners and farmers are interested in rock flours with higher paramagnetic activity.
Basalt rocks can – depending on their origin and composition – have different strengths of paramagnetic properties. Therefore, the paramagnetic value is also given for some basalt flours.
If you would like to delve deeper into this topic - it is super exciting - you will find a detailed explanation in these two articles:
🔗 Paramagnetism in basalt primary rock meal
🔗 Interview: Phil Callahan and Graeme Sait - Revolutionary perspectives on Paramagnetism in Agriculture
Applying basalt meal in the garden
Basalt meal is primarily used in the garden to:
- provide long-term trace elements to soils
- enrich compost with minerals
- support soil processes
The fine basalt meal powder can be easily sprinkled on beds, even sprayed or mixed with compost. The basalt granulate, as we call it, can be easily processed in energy towers or, as in our blog title image, for tree strengthening.
TIP: Check the paramagnetic value. There are big differences here. And yes, it can be measured.
Zeolite
Zeolite differs significantly from classic rock flours.
While basalt meal or primary rock meal primarily provides minerals, zeolite has an exceptional crystal structure with countless microscopic cavities. This so-called microporous structure arises when volcanic ash and lava react with water over geological periods and transform into stable crystal lattices.
The result is a mineral with a fascinating internal structure: a network of fine channels and cavities that can absorb water and dissolved substances. And of course, it carries the energy of primeval water within it.
This structure gives zeolite several special properties.
Firstly, zeolite can store water. Water can be absorbed into the pores of the mineral and released again when needed. Especially in garden soils or raised beds, this property can help to keep the water supply of the plants more stable.
Secondly, zeolite can bind nutrients in the soil. Certain nutrient ions can be adsorbed on the surface of the mineral and thus remain available in the soil for longer. This process is referred to in soil science as ion exchange capacity.
Another important aspect is the enormous internal surface area of zeolite. A single gram of this mineral can have a surface area of several hundred square meters. If it has been tribomechanically ground, an even much larger one. This structure offers ideal conditions for microorganisms to settle there and play an important role in soil life.
Silicon as the main element
In addition, zeolite - like many volcanic minerals - contains a variety of trace elements. Particularly noteworthy is its content of silicon, an element that can play an important role for plants. Silicon can contribute to the stability of plant cell structures and is increasingly being investigated in plant physiology.
The origin of zeolite is also remarkable. The mineral is formed from volcanic material that once emerged from lava flows and ash clouds. Fire, rock and water interact over long periods of time and form the characteristic crystal structure of zeolite. In a way, this mineral thus carries the geological history of its formation within itself - emerged from the energy of volcanic processes and transformed into stable crystals over millennia.
Due to these properties, zeolite is now frequently used as a mineral soil improver. Many gardeners use zeolite in garden soil, in raised beds or when planting young plants to better retain water and nutrients in the soil, while also supporting soil life and imbuing the soil with these energy qualities.
TIP: Pay attention to the particle size. The finer the material, the more plant-available AND the surface area is maximal if the material is not sieved but tribomechanically ground.
More explanation on the effect and application can be found in the following articles:
🔗 Zeolite in the garden correct application
🔗 Effect of zeolite in the soil - Scientific basics
Lime
Lime is one of the most important mineral soil conditioners in the garden. Its main task is to regulate the pH of the soil and thus influence important chemical processes in the soil.
The pH value describes whether a soil is rather acidic, neutral or alkaline. Many garden plants prefer a slightly acidic to neutral soil. However, if the soil becomes too acidic over the years, certain nutrients may become less available to plants.
The slow acidification of soils is a completely natural process. This is contributed to, among other things, by:
- rain and leaching of minerals
- plant growth
- the breakdown of organic matter by microorganisms
Intensive gardening can also lead to the soil gradually becoming more acidic. If the pH value is too low, plants can absorb important nutrients such as calcium, magnesium or phosphorus less well. At the same time, other substances in the soil can become more soluble and impair plant growth.
This is where lime comes in.
By applying lime, the soil is de-acidified, the pH value rises again and many nutrients become more available to plants. At the same time, lime can improve soil structure, especially in heavy soils. Clay particles can combine more stably into crumbs through calcium, making the soil looser and better aerated.
Soil life also reacts to pH. Many microorganisms that decompose organic matter and release nutrients are most active in soils with a balanced pH. Targeted liming can therefore also support the activity of soil life.
However, an important rule applies when liming: Not every soil needs lime.
While some soils are indeed too acidic and benefit from liming, others already have an appropriate or even slightly alkaline pH. In such cases, additional liming would do more harm than good.
Therefore, it is advisable to know the pH of the soil before applying lime. A simple soil analysis can be very helpful here.
In addition, it is useful to always consider lime in connection with other mineral soil improvers. While lime mainly influences the pH value, other materials - such as zeolite or rock flours - fulfill completely different functions in the soil.
Understanding garden soil better: a soil analysis
Before using mineral soil improvers in the garden, it can be useful to get to know the soil better. A simple soil analysis provides information about important properties such as the pH value, nutrient supply and soil structure.
This knowledge is particularly helpful when applying lime. While some soils are indeed too acidic and benefit from liming, others already have a suitable pH value. In such cases, additional liming would not be necessary.
A soil analysis therefore helps to use mineral soil improvers more targeted and to keep the garden soil in balance in the long term.
Dolomite
Dolomite is a rock that contains both calcium and magnesium.
Dolomitic lime or magnesium lime is often used when soils have a magnesium deficiency in addition to the lime requirement.
Magnesium is an important component of chlorophyll and plays a central role in photosynthesis. Dolomite can therefore both regulate the pH value and supply magnesium.
TIP: The finer, the more effective and sustainable, because you need to use less. The particle size is indicated in micrometers (µm).
A detailed explanation of the different effects of these mineral substances can be found here:
🔗 Lime, Zeolite and Rock Flours – how they work in the soil
Vermiculite
Vermiculite is a natural mineral that originates from certain clay minerals and possesses a remarkable property: when heated strongly, it expands and forms a very light, porous structure.
This process creates small, layered particles with numerous cavities. This structure makes vermiculite a very interesting material in horticulture, especially when it comes to water balance and soil structure.
Unlike classic rock flours, vermiculite is not primarily used for its minerals, but for its physical properties in the soil.
The most important properties of vermiculite are:
- very good water retention
- loose and airy structure
- good aeration of substrates
- even moisture distribution
Due to its ability to absorb water and release it slowly, vermiculite is often used in potting substrates. This property can be particularly helpful when growing young plants, as young roots are very sensitive to strong fluctuations in moisture.
Vermiculite can also help to retain water longer in the substrate in dry soils or in planters. This can keep the soil moisture more stable, which can be particularly advantageous in warm summer periods.
If you are interested in the properties of this mineral in more detail, you will find a comprehensive explanation here:
🔗 Vermiculite – Water storage for dry soils
Vermiculite compared to zeolite
While vermiculite is primarily known for its ability to store water, zeolite also has a special property: it can also bind nutrients in the soil.
Both minerals can therefore fulfill different tasks in the garden and are sometimes even combined. Take a look at the water storage pellets.
Leonardite
Leonardite differs significantly from classic rock flours such as basalt or lime. While these primarily supply minerals or influence the pH of the soil, another property is at the forefront with leonardite: its high content of humic substances.
Leonardite is formed from very old plant deposits that have been converted over geological periods under pressure and exclusion of oxygen. It can be understood as a kind of naturally concentrated form of organic soil substance. In contrast to fresh humus or compost, however, leonardite is already highly stabilized and contains a particularly large number of humic acids and fulvic acids.
These humic substances play an important role in the soil. They can:
- stabilize the soil structure
- increase the soil's ability to store water
- bind nutrients in the soil
- support microorganisms in the soil
- carry the knowledge of primeval microbiology within them
Humic acids act in the soil somewhat like a natural nutrient buffer. They can absorb nutrients and release them later, making them available to plants for longer.
Furthermore, humic substances also influence the soil structure. They promote the formation of stable soil crumbs and can thus help to keep the soil looser and better aerated. Especially in leached or structurally weak soils, leonardite can therefore be interesting.
Another important effect concerns soil life. Many microorganisms use humic substances as an energy source or benefit from the improved soil structure. Thus, leonardite can indirectly contribute to the activity of soil life.
For these reasons, leonardite is often used in soils that are losing humus in the long term or in which soil life is to be strengthened.
A detailed explanation of the effect of leonardite and mineral earths in connection with soil health can be found here:
🔗 Leonardite and mineral earth – natural support for healthy soils
Why not all rock flours work the same
Many of these materials are grouped together under the collective term "rock flour" in the garden. However, their mode of action differs significantly. And they can complement each other well.
A simplified overview:
- Basalt meal → provides minerals and has paramagnetic properties
- Lime → regulates the pH value
- Dolomite → supplies calcium and magnesium
- Vermiculite → stores water, lots of water
- Leonardite → provides humic acids and the energy of primeval earth
- Zeolite → stores water and nutrients, can bind toxins
Knowing these differences allows you to make more targeted decisions about which materials are useful in your own garden.
Which mineral helps with which soil problem?
| Soil problem in the garden | Mineral support | Effect in the soil |
|---|---|---|
| Soil is too acidic | Lime | raises the pH and improves nutrient availability |
| Magnesium is missing in the soil | Dolomite | supplies calcium and magnesium |
| Soil quickly loses nutrients | Zeolite | binds nutrients and reduces leaching |
| Soil dries out quickly | Zeolite / Vermiculite | stores water in the soil |
| Soil contains few trace elements | Basalt meal / primal rock meal | supplies minerals and trace elements |
| Soil life is weak | Leonardite | supplies humic acids and supports microorganisms |
| Soil structure is poor | Mineral earth / clay minerals | stabilize soil crumbs and improve structure |
| Potting soil dries out quickly | Vermiculite | stores water and loosens substrate |
From our practice at Steinkraft
At Steinkraft, we have been working with natural minerals and their effect on the soil for many years. Our approach is simple: from nature – for nature. In our daily work with zeolite, basalt and other mineral raw materials, we constantly see how strongly quality, origin and processing can influence the properties of these materials.
Part of our knowledge comes from scientific literature and studies, another part from practical experience – also on our own soils. We share this knowledge in the Steinkraft Blog to show how natural minerals can contribute to living soils and sustainable garden cycles.
🔗 More knowledge about zeolite, rock flours and natural soil care can be found in the Steinkraft Zeolite Blog - Garden
Conclusion: Minerals can specifically support garden soil
Mineral soil conditioners do not replace good soil care. A living soil is created primarily by organic matter, microorganisms and stable structures.
But various minerals can specifically support these processes. While lime or dolomite regulate the pH and supply important nutrients, zeolite, vermiculite or mineral earths primarily improve water and nutrient storage in the soil.
Anyone who understands the different modes of action can use these materials specifically – and thus create the long-term basis for healthy plants and living garden soil.
Ultimately, not only plants and soil life benefit from this – but also the quality of the food that grows in healthy garden soil. So do we.
If you would like to try out various mineral soil conditioners in your garden, you will find a selection of natural products in our
🔗 Collection for zeolite and mineral soil improvers in the garden.
Read more about zeolite in the garden
👉 Why zeolite works in the soil – ion exchange, water and nutrients
👉 Zeolite in raised beds – support for loose and nutrient-rich soil
👉 Zeolite and nutrients in the soil
👉 Zeolite explained simply - actually explained for children
👉 The garden in spring – how healthy abundance in the soil is created
👉 Stress-free young plants into life
👉 Rock flours in the garden - basalt, zeolite, lime, leonardite, dolomite and other minerals correctly understood
👉 Application and dosage of zeolite in the garden
