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Perma Guard Fossil Shell Flour is food-grade diatomaceous earth milled from a freshwater deposit of the diatom Aulacoseira, laid down in the Miocene epoch. The fossil shells are amorphous silica, hard enough not to dissolve in liquid, and their porous walls absorb moisture, which is why it works as an anti-caking agent and a mechanical insect control. It suits households treating cracks, carpets and pet bedding, gardeners, and people mixing it into grain or feed. Against darker, clay-heavy diatomaceous earths, it is a purer, lighter powder; against chemical insecticides it is slower-acting and needs dry conditions to keep working.
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Lowest price we've seen: $35.00 on Nov 1 at Hefty Harvest; highest $37.99 on Nov 13. Tracked across 4 stores since Nov 1.
Buyers rate it highly and describe it as a fine, light powder that works for pest control and as a feed additive. Complaints center on the dust it raises during application.
Perma Guard Diatomaceous Earth is packaged under the FOSSIL SHELL FLOUR® label. It comes from a very pure fresh water deposit of the diatom Aulacoseira. The deposit was created in the Miocene epoch.
The diatom's shell is made of amorphous silica. Its shape and hardness are important to how it works. The hardness keeps it from dissolving in liquid.
Holes along the diatom's wall let it absorb moisture, which is why it is used as an anti-caking agent. Darker colored diatomaceous earth often contains an excess of a mineral such as iron or a high percentage of clay.
