If you’ve ever been to a rock show or dealt with mineral dealers, you might have come across specimens labeled “enhydros.” Often, these are quartz crystals with small liquid inclusions that contain tiny moving bubbles.
When you tip the crystal back and forth, the bubble inside moves, and dealers will frequently highlight this feature, even using magnifiers to help you spot it. But are these truly enhydros? Let’s delve into the science to understand what these fascinating inclusions really are.
What Are Fluid Inclusions?
(Click To See The Fluid Inclusions)
What many mineral dealers are selling as “enhydros” are actually fluid inclusions. Fluid inclusions form during the growth of quartz crystals, commonly from hot groundwater containing dissolved silica. As the crystal grows, small pits or cavities may develop on the surface due to uneven growth. These cavities can trap liquid from the surrounding environment. When the crystal cools after formation, the trapped liquid contracts and often forms a small vapor bubble.
(Click Image To See The Fluid Inclusions)
Scientists refer to these features as fluid inclusions. They’re found in many minerals, not just quartz, and can contain water, salty brine, oil, or even microscopic crystals like halite. For example, quartz crystals from the famous Herkimer diamonds in New York may contain carbon-rich fluids, while fluorite from Tennessee can trap oil, which even fluoresces under UV light!
(Click Image To See The Fluid Inclusions)
Fluid inclusions are not rare, and they play a significant role in mineralogy. The liquid inside these inclusions is a literal time capsule, preserving the conditions under which the mineral formed. By studying these inclusions, scientists can gain valuable insights into the formation of minerals, ore deposits, and even ancient geochemical environments.
The Science Behind Fluid Inclusions
When a crystal forms, its outer surfaces, edges, and corners grow at different rates. These inconsistencies create small pockets that trap the liquid around the crystal. As the crystal cools, the liquid inside the inclusion contracts and pulls away from the walls of the cavity, creating a small vapor bubble. The trapped liquid, whether it’s water, saltwater, or oil, remains sealed inside the crystal for millions, if not billions, of years.
Fluid inclusions can even hold microscopic crystals. For example, salty water trapped in a quartz crystal may cool and form tiny halite crystals. These inclusions are fascinating to observe under a microscope and provide mineral collectors and scientists with hours of intrigue.
What Is an Enhydro?
So, what exactly is an enhydro? According to the American Geological Institute’s Glossary of Geological Terms, an enhydro is defined as “a hollow nodule or geode of chalcedony containing water, sometimes in large amounts.” This is distinct from the fluid inclusions we’ve been discussing. Enhydros form in microcrystalline quartz (chalcedony), which grows from silica-rich groundwater flowing through volcanic rock. As the chalcedony fills a cavity, it can trap water inside, forming a geode with liquid.
When a true enhydro is found, the water inside is often free to move around within the hollow nodule. Dealers cut these geodes in a way that preserves the water, and if you shake the enhydro, you can hear or see the water sloshing around. Unlike fluid inclusions, enhydros may leak water over time, as their walls are porous.
Key Differences Between Fluid Inclusions and Enhydros
The main difference between fluid inclusions and enhydros lies in the way they form and the nature of the liquid trapped inside:
- Fluid Inclusions: These are microscopic pockets of liquid trapped inside a mineral as it grows. The liquid is often from the environment in which the crystal formed and remains sealed in the mineral’s non-porous structure. The bubble inside moves because of the difference in expansion between the liquid and the mineral as they cool after formation. Fluid inclusions can be millions or even billions of years old.
- Enhydros: These are geodes or nodules of chalcedony containing liquid, typically water, trapped in a central cavity. The liquid may not be the original water trapped during formation, as the porous walls of the geode can allow water to flow in and out over time.
Why Does It Matter?
From a scientific perspective, the difference is significant. Fluid inclusions are valuable research tools, acting as time capsules that preserve the conditions of mineral formation. They help scientists understand how minerals and ore deposits form and can even guide exploration for oil and metal deposits. In contrast, enhydros are curiosities, intriguing but not as scientifically useful.
For mineral collectors, fluid inclusions can enhance the value of a specimen because they offer a glimpse into the ancient processes that formed the mineral. However, it is important to label them correctly. Quartz crystals with fluid inclusions should be identified as such, rather than mislabeled as enhydros.
The Fascination of Fluid Inclusions
Watching the bubble move inside a crystal is undeniably mesmerizing, and fluid inclusions are a popular feature among collectors. I have an amethyst crystal from Namibia with a large fluid inclusion that you can see without a magnifier. The bubble moves around its triangular home when you rotate the crystal, offering endless fascination.
While enhydros hold water in a larger, hollow cavity, fluid inclusions trap liquid in a solid, non-porous structure. They preserve the actual fluid from the time the mineral was growing, and some fluid inclusions are as old as the Precambrian era, holding water that is over three billion years old. That’s amazing!
In summary, while both enhydros and fluid inclusions are captivating, they are distinctly different. Fluid inclusions offer scientific insights and add value to specimens, whereas enhydros are geological curiosities that might slowly lose their liquid over time. Understanding this difference ensures that you can better appreciate the unique qualities of each and properly label your mineral collection. Now, go ahead and update those labels at the next rock show!
