One of the things that makes natural sandstone paving so distinctive is that no two slabs are exactly the same. Colours, textures, veins and natural markings can vary considerably from one piece of stone to another.
Occasionally, you may even come across something that looks like it has been preserved in the stone for millions of years.
Fossils in sandstone can occur naturally. However, not every plant-like marking found in a sandstone paving slab is actually a fossil. Some of the striking fern, leaf or tree-like patterns seen in natural sandstone may instead be mineral formations known as dendrites.
So, how can you tell the difference – and what exactly are you looking at when unusual markings appear in your sandstone paving?
Fossils in Sandstone: Can Sandstone Contain Fossils?
Yes, genuine fossils can be found in sandstone.
Sandstone is a sedimentary rock. It forms when layers of sand and other sediment accumulate over time before eventually becoming compacted and cemented together into stone.
Because sedimentary rocks form gradually from deposited material, they can sometimes preserve evidence of ancient life.
Depending on where the sandstone formed and the environment at the time, fossils found in sedimentary rock can include shells, plant remains, impressions, burrows and other traces left behind by organisms.
This means that finding fossils in sandstone is certainly possible.
However, one of the interesting things about natural stone is that geological processes can also create patterns which look surprisingly similar to fossils.
What Are the Fern-Like Markings in Sandstone?
Take a look at the sandstone paving shown in these photographs.
Across several of the slabs are dark, branching patterns that look remarkably like ferns, small trees or leaves.
It’s easy to understand why someone would immediately assume they were looking at fossilised plants.
Within the paving industry, markings like these may often be described as fossil markings. However, many similar fern-like formations found in natural stone are actually mineral dendrites.
Mineral dendrites are naturally occurring deposits that form branching patterns within or across the surface of stone.
Because the finished patterns resemble plants so closely, they are sometimes described as pseudofossils – geological formations that look like fossils but were not formed by a living organism.
What Are Mineral Dendrites?
Dendritic markings are generally associated with minerals containing manganese or iron.
Over long periods, mineral-rich water can move through tiny cracks, pores or bedding planes within the stone.
As minerals are deposited, they can spread out into fine branching formations.
The resulting shapes often resemble:
- Ferns
- Leaves
- Tree branches
- Moss
- Roots
In some sandstone slabs, the markings are small and subtle. In others, they can spread across a large section of the stone and become one of the most noticeable features of the paving.
The effect can be extremely convincing, which is why mineral dendrites have historically been mistaken for plant fossils.
From a photograph alone, it isn’t always possible to identify a particular geological marking with complete certainty. The origin and composition of the stone would need to be considered for a definitive identification.
That’s why it’s better to think of these markings as fossil-like natural features unless their geological origin has been confirmed.
Fossil or Pseudofossil: What's the Difference?
The main difference is how the marking was created.
A fossil is evidence of something that was once alive.
That could mean the remains of an organism itself, or a trace it left behind, such as an impression, footprint or burrow.
A pseudofossil, on the other hand, is created through natural geological or mineral processes but happens to resemble something biological.
Dendritic mineral formations are one of the best examples.
When we see a branching shape that resembles a fern or plant, our brain naturally interprets it as something organic. In reality, the pattern may have been created entirely by minerals moving through the stone.
Either way, it provides an interesting insight into the natural history of the sandstone.
Are Fossil-Like Markings in Sandstone a Defect?
No.
Natural colour variation, mineral deposits, veining and other geological markings are all part of the character of genuine natural sandstone.
Unlike manufactured paving, natural sandstone isn’t produced under controlled factory conditions where every slab is designed to look identical.
Variations can include:
- Different colours and tones
- Natural veining
- Surface texture
- Bedding patterns
- Mineral deposits
- Fossils or fossil-like formations
- Natural banding
Even slabs from the same pack can look noticeably different.
In the paving shown below, for example, some stones have only small areas of dark branching detail, while others contain dramatic patterns across a significant part of the slab.
These variations are not necessarily imperfections. They’re part of what makes natural stone exactly that – natural.
Should You Try to Remove These Markings?
Before attempting to remove an unusual mark from sandstone paving, it’s important to work out whether you’re dealing with a surface stain or a natural characteristic of the stone.
Dirt, algae and other organic growth sit on or close to the surface and can usually be treated with an appropriate cleaning method.
A mineral formation within the sandstone is different.
If the marking forms part of the natural stone itself, cleaning products are unlikely to remove it in the same way they would remove surface contamination.
Using aggressive cleaners or excessive pressure in an attempt to remove a natural marking could instead alter the appearance of the surrounding sandstone.
If you’re unsure what has caused a mark on natural paving, it’s always best to establish what you’re dealing with before attempting to treat it.
Natural Variation Is Part of Sandstone's Appeal
One of the main reasons people choose sandstone paving is its natural character.
A patio can contain a mixture of creams, buffs, browns, pinks and greys, along with veins, mineral deposits and other variations created as the stone formed.
That’s also why natural sandstone should be viewed as a complete installation rather than judging each slab individually.
When laying natural stone, mixing slabs from different packs can help distribute changes in colour and pattern throughout the patio, creating a balanced overall finish.
Features such as fossil-like markings can then become part of the character of the finished space rather than appearing concentrated in one area.
Millions of Years of Geology Beneath Your Feet
Finding what appears to be a fossil in sandstone is a reminder of just how different natural stone is from a manufactured paving product.
Before a sandstone slab was ever quarried, cut and installed in a garden, the rock had already been shaped by geological processes taking place over an enormous period of time.
Some markings may genuinely preserve evidence of ancient life.
Others may simply be mineral formations that happen to look incredibly similar.
Either way, the colours, patterns and markings found in natural sandstone help tell the story of how the stone was formed.
So, the next time you notice what looks like a tiny fern, tree or leaf hidden within your sandstone paving, take a closer look.
It could be a fossil.
Or it could be geology doing a very convincing impression of one.
Working With Natural Sandstone Paving?
Whether you’re installing a new sandstone patio or maintaining an existing one, it’s important to use products that are suitable for both the natural stone and the construction of the paving.
Joint-It offers a range of professional jointing and stone care products for outdoor paving.
Explore the Joint-It range or use our Store Locator to find your nearest Joint-It stockist.
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