Diatomaceous earth (scientific name: diatom melosira preicelanica) has become increasingly popular with Australian gardeners, growers and property owners looking for a versatile, naturally occurring mineral product for insect control. But when you start comparing products and reviews, you'll quickly discover that not all diatomaceous earth is the same.
The source of the diatomaceous earth, the type of fossilised diatoms it contains, how it has been processed, and its silica composition can all vary between products.
This is one reason Soil Solutions stocks Perma-Guard Food Grade Diatomaceous Earth – Fossil Shell Flour.
Perma-Guard's Fossil Shell Flour®, also known as Perma Guard diatomaceous earth, is a natural, uncalcined diatomaceous earth sourced from a freshwater deposit in the United States. Its manufacturer identifies the deposit as consisting predominantly of fossilised Aulacoseira diatoms and describes the product as being rich in amorphous silica.
So, what does all of that mean, and what should you actually look for when comparing diatomaceous earth products?
What Is Perma-Guard Diatomaceous Earth?
Diatomaceous earth, often abbreviated to DE, is a naturally occurring fossil shell powder material formed from the fossilised remains of microscopic aquatic organisms called diatoms.
Over very long periods, the silica-rich skeletal structures of these organisms can accumulate into deposits that can be mined, dried, milled and processed into the fine powder we know as diatomaceous earth.
However, individual deposits aren't identical.
Different deposits can contain different species of diatoms, mineral compositions and amounts of other naturally occurring material. The way the material is subsequently processed also matters.
Perma-Guard markets its natural diatomaceous earth under the registered name Fossil Shell Flour®.
According to Perma-Guard, its Fossil Shell Flour comes from a freshwater deposit formed during the Miocene epoch and predominantly contains fossilised Aulacoseira diatoms.
What Is Fossil Shell Flour?
The term Fossil Shell Flour® is Perma-Guard's name for its particular natural diatomaceous earth fossil shell product.
It isn't a completely different substance from diatomaceous earth. Rather, it identifies Perma-Guard's specific product and source.
Backed by the National Library of Medicine's recent reviews, fossil shell flour is a non-toxic, affordable and widely available natural material found in substantial deposits across many parts of the world. In recent years, its distinctive insecticide properties have also led to its use as an additive in a growing range of applications.
The material consists of microscopic fossilised diatom structures that contain trace minerals that have been mined and finely milled.
Perma-Guard's current product label describes Fossil Shell Flour as a natural product composed of ground diatomaceous earth, specifically amorphous silica of freshwater origin.
Its Safety Data Sheet (SDS) lists the composition as 100% natural diatomaceous earth and identifies the silica as amorphous and uncalcined.
These characteristics are important when comparing it with other types of diatomaceous earth.
1. Perma-Guard Fossil Shell Flour Comes From a Freshwater Deposit
One of the most distinctive characteristics of Perma-Guard Fossil Shell Flour is its geological source. The product comes from a freshwater diatomaceous earth deposit rather than a marine deposit.
Perma-Guard identifies the predominant fossilised diatom in its deposit as Aulacoseira. These diatoms have a distinctive porous, tubular structure.
The manufacturer says this deposit has a relatively consistent diatom composition and that the physical structure of the fossilised shells contributes to the material's absorptive properties.
However, freshwater origin shouldn't be treated as a guarantee that one diatomaceous earth product is automatically superior to another.
Perma-Guard food grade fossil shell flour is safe and commonly used in animal environments, including housing, bedding and surrounding areas, and can also be used in the garden.
The characteristics of the individual deposit, mineral composition, processing method and finished product specifications are more useful things to examine when comparing products.
We'll explore this subject in more detail in our guide to Freshwater vs Marine Diatomaceous Earth.
2. It Contains Predominantly Amorphous Silica
Silica is one of the main components of diatomaceous earth, but the form of silica matters.
Perma-Guard describes Fossil Shell Flour as containing approximately 89–92% amorphous silica.
Amorphous silica has a different physical structure from crystalline silica.
This distinction becomes particularly important when comparing natural food-grade diatomaceous earth with products manufactured for applications such as swimming-pool filtration.
Pool-grade diatomaceous earth is typically subjected to high-temperature processing known as calcination. This changes the characteristics of the material and can substantially increase its crystalline silica content.
Perma-Guard Fossil Shell Flour, by comparison, is uncalcined.
The current Perma-Guard SDS states that Fossil Shell Flour contains less than 0.1% crystalline silica.
This is an important specification to check rather than assuming that every bag labelled "diatomaceous earth" has the same composition.
For a more detailed explanation, read our guide to Food-Grade vs Pool-Grade Diatomaceous Earth: What's the Difference?
3. The Shape of the Diatoms Matters
Under a microscope, diatomaceous earth isn't simply ordinary dust.
The fossilised diatom structures contain microscopic pores and complex shapes.
Perma-Guard's deposit predominantly contains Aulacoseira diatoms, which have a cylindrical or tubular structure with numerous microscopic pores.
According to the manufacturer, this structure provides a relatively large surface area and contributes to the material's ability to absorb moisture.
Perma-Guard's Certificate of Analysis lists a typical surface area of approximately 35.7 m² per gram, illustrating just how much microscopic surface area can exist within the finely milled material.
These physical properties are among the reasons diatomaceous earth has applications ranging from anti-caking uses to horticultural and agricultural applications.
Under a microscope, diatomaceous earth isn't simply ordinary dust.
The fossilised diatom structures contain microscopic pores and complex shapes.
Perma-Guard's deposit predominantly contains Aulacoseira diatoms, which have a cylindrical or tubular structure with numerous microscopic pores.
According to the manufacturer, this structure provides a relatively large surface area and contributes to the material's ability to absorb moisture.
Perma-Guard's Certificate of Analysis lists a typical surface area of approximately 35.7 m² per gram, illustrating just how much microscopic surface area can exist within the finely milled material.
These physical properties are among the reasons diatomaceous earth has applications ranging from anti-caking uses to horticultural and agricultural applications.
4. It's Minimally Processed Rather Than Calcined
Processing is another important difference between diatomaceous earth products.
Perma-Guard describes the production of Fossil Shell Flour as essentially involving mining the natural deposit before the material is dried, ground, sifted and packaged.
It isn't subjected to the high-temperature calcination used to manufacture some industrial and filtration-grade diatomaceous earth products.
That distinction helps preserve the material as predominantly amorphous silica rather than converting significant amounts into crystalline forms.
This is also why food-grade and pool-grade diatomaceous earth should never be considered interchangeable products.
Always check the product label and specifications before purchasing DE for a particular purpose.
5. Purity and Consistency Are Important
When purchasing diatomaceous earth, colour alone isn't a reliable measure of quality.
DE deposits naturally vary because their geological environments vary.
Depending on the deposit, diatomaceous earth may contain different proportions of clay, iron and other naturally occurring minerals.
Perma-Guard describes its Fossil Shell Flour as generally almost white when dry and light tan when wet. The company attributes this partly to the characteristics and consistency of its particular freshwater deposit.
Rather than judging a product purely by appearance, look for documented information such as:
- whether the product is natural or calcined
- the source of the diatomaceous earth
- amorphous and crystalline silica information
- a current Safety Data Sheet
- manufacturer specifications
- intended uses
- clear product labelling.
This gives you much more useful information than marketing terms such as "premium" or "superior" without supporting specifications.
6. Food Grade Doesn't Mean Dust Should Be Inhaled
This is an especially important distinction.
The term food grade doesn't mean that airborne diatomaceous earth dust is harmless to breathe.
Perma-Guard's SDS specifically advises users to minimise dust generation and accumulation and avoid breathing the dust. It also notes that dust can cause temporary eye irritation and that prolonged or repeated exposure to excessive concentrations of dust can affect the lungs.
When using diatomaceous earth around the garden or property, avoid creating airborne clouds of powder and follow the handling directions on the product label.
You can learn more about responsible handling in our guide Is Diatomaceous Earth Safe Around Pets, Plants and People?
What Should You Compare When Buying Diatomaceous Earth?
Rather than choosing diatomaceous earth based purely on price, compare the actual specifications.
Check whether you can determine:
· Source: Is the DE from a documented deposit?
· Processing: Is it natural/uncalcined or has it been heat treated?
· Silica composition: Does the manufacturer provide information about amorphous and crystalline silica?
· SDS: Is there a Safety Data Sheet available?
· Product grade: Is the product clearly labelled for its intended use?
· Manufacturer: Can you identify who produces the material?
· Consistency: Does the supplier provide specifications rather than relying entirely on broad marketing claims?
This is particularly important when comparing inexpensive DE products online where the origin and processing method aren't always clearly stated.
Why Does Soil Solutions Stock Perma-Guard?
For Soil Solutions, the advantage of Perma-Guard isn't simply the brand name.
It's the amount of information available about the product.
Perma-Guard provides documentation identifying the source and type of diatomaceous earth, its processing method, silica composition, physical characteristics and appropriate handling precautions.
That makes it easier for customers to understand what they're actually buying.
For gardeners in particular, knowing the difference between natural food-grade DE and heavily processed filtration-grade products is far more useful than simply seeing "diatomaceous earth" printed on a bag.
Soil Solutions supplies Perma-Guard Fossil Shell Flour Food Grade Diatomaceous Earth for customers looking for a documented, natural freshwater DE product.
View Perma-Guard Food Grade Diatomaceous Earth at Soil Solutions
Frequently Asked Questions
Is Perma-Guard the same as ordinary diatomaceous earth?
Perma-Guard Fossil Shell Flour is diatomaceous earth, but it comes from a specific freshwater deposit and has documented characteristics. The manufacturer identifies its deposit as predominantly containing Aulacoseira diatoms and approximately 89–92% amorphous silica. Other DE products may come from different deposits or undergo different processing.
What does Fossil Shell Flour mean?
Fossil Shell Flour® is Perma-Guard's registered product name for its natural freshwater diatomaceous earth. The material itself consists of the finely milled fossilised remains of microscopic diatoms.
Is Perma-Guard diatomaceous earth food grade?
Perma-Guard labels Fossil Shell Flour as Food Chemical Codex Grade. Its manufacturer supplies it for uses including an anti-caking agent in animal feed, subject to the directions and limits on the product label. Always use the product according to its labelled purpose and applicable Australian requirements.
Is Perma-Guard the same as pool-grade diatomaceous earth?
No. Perma-Guard Fossil Shell Flour is natural, uncalcined diatomaceous earth composed predominantly of amorphous silica. DE manufactured for swimming-pool filtration is processed differently and can contain substantially more crystalline silica. The two products shouldn't be treated as interchangeable.
Is Perma-Guard diatomaceous earth safe to breathe?
You should avoid breathing diatomaceous earth dust. Perma-Guard's SDS recommends minimising dust generation and avoiding inhalation and eye contact. "Food grade" doesn't mean that fine airborne mineral dust should be deliberately inhaled.
Choosing Diatomaceous Earth With Confidence
The most important takeaway is simple: diatomaceous earth is a category of material, not one universally identical product.
Its geological source, diatom composition, processing and silica profile can differ.
Perma-Guard Fossil Shell Flour stands out because these characteristics are documented. It comes from a freshwater deposit, predominantly contains fossilised Aulacoseira diatoms, is uncalcined, contains a high proportion of amorphous silica and is supported by manufacturer specifications and an SDS.
For Australian gardeners comparing DE products, those are useful, verifiable characteristics to consider — without needing to rely on unsupported claims that one product is universally "the best."
Shop Perma-Guard Food Grade Diatomaceous Earth – Fossil Shell Flour at Soil Solutions