Like the rings of a tree, the incredible patterns of this mineral are a look into the past, with each band representing millions of years.

This is travertine, a limestone rock that forms in deep caves and hot springs. As water moves through these places, it can leave behind tiny particles of calcium carbonate. Over time, they build up into solid rock which mimics the patterns of the ancient water flow.

Travertine's beauty and strength have been admired by builders for millennia. A spring outside of Rome has been mined for over 2,000 years for travertine, which was used in the construction of buildings like the Colosseum and St. Peter's Basilica.

This specimen is a unique travertine speleothem segment. These incredible stones are created by water flows over millions of years and every piece has a unique and beautiful pattern. A speleothem is a type of rock formation made from flowing water and includes stalactite, stalagmites, flowstones, columns, and flow terraces. The unique shapes etched onto their surface shows how the water deposited the stones over millions of years.

Colors, shapes, and sizes range due to the formation of this stone, but pieces range from about 2 to 3 inches, with marble, gold, and caramel colorings. Each specimen ships in a sturdy packing carton along with an acrylic stand. An informational card which serves as certificate of authenticity is also included.

What's the blue? Some pieces show small blue markings from the polishing process. This residue is totally normal and not of any issue to the specimen.

If you ever come across a roiling hot spring, you’d do well to check along the edges of the water for a very special kind of rock. Travertine is a limestone that forms around geothermal springs, owing to the high temperatures and rich mineral concentrations found there. It can also be found around lakes and rivers with high calcium concentrations, or dangling from the ceiling of a cave as stalactite.

Travertine forms when geothermically charged hot springs carry carbon dioxide-rich water up from beneath the Earth’s surface. When it reaches the atmosphere, the CO2 dissipates, leaving calcium carbonate behind to interact with limestone. The porous rock is the perfect vector for the CO2-rich water, producing a reaction between the carbonic acid of the water and carbonate rock, producing calcium bicarbonate and travertines.

Travertine can also form in limestone caves as a speleothem, a beautiful type of rock formation created by flowing water. These speleothems can appear as stalactites, stalagmites, flowstones, columns, or terraces, and create unique and haunting caves.

Calcium-carbonate-rich waters drip from the ceiling of the cave, then falling to the ground, leaving minerals from both where it fell and landed. This is the process behind stalactites and stalagmites. Flowing water can also leave behind traces of calcium carbonate in its path, making long almost staircase-shaped or draped formations.

The effect is beautiful, with speleothems appearing almost soft and silken. In a way, it's like the stone is following the path of water, only over the course of millions of years. The process is similar to travertine formation on the surface, but with the closed environment of the cave causing the travertine to form in beautiful towering pillars.

The word "travertine" comes from a corruption of the Latin Tivertino, named for Tivoli, an area in central Italy where travertine is abundant. It’s noted by Pliny the Elder in Naturalis Historia as a particularly strong rock, and was used throughout Rome and the rest of the world as a building material. The mineral is even important enough to have left its mark in some pieces of classical literature.

The strength and beauty of the stone has captured the eye of architects for thousands of years. In fact, today you can find travertine in constructions like the Colosseum and St. Peter's Basilica!

Travertine is also useful to paleontologists. The travertine formation process can preserve animals and plants, slowly encasing them in stone over millions of years of waterflow. These fossils can manifest as either preserved bones or an encrustation, a limestone mold preserving the shape of the decayed organism like a cocoon.

Travertine also provides scientists the ability to estimate the Earth’s climate at the time of the specific rock’s formation, as its formation is contingent on the atmosphere’s CO2 levels at the time. Travertine sites are also known to support an abundance of microscopic life, owing to the chemically rich waters to be found there. These run the gamut from prokaryotic, single-celled organisms, all the way up to horsetail ferns and other plant life that in turn provide food sources for animals.

Travertine is in fact an incredibly dynamic stone, one that forms from the flow of water and even supports its own ecosystem and food web. This stone is a reminder of the breadth of the environment, how even rock deposits play a role in sustaining and nurturing life.