First things first…. ”Enhydros” is a bit of a misnomer. It is a trade name given to minerals that have fluid inclusions, which would be all fine and great except that Enhydros are already a thing* so it can be a little confusing if you are doing a geology/mineralogy deep dive. If you are not looking to get all nerdy and just want to browse for cool stones and jewelry with million+ year old time capsules inside, then asking for/searching for enhydros will probably get you what you’re after. Sorry to start this one off on the pedantic side, but actually no I’m not. On to the fun stuff!
an amethyst a prominent fluid inclusion // B. DeCamp via mindat.org
Quartz crystals are commonly formed in underground hydrothermal environments, picture a cave or large cavity filled with hot water that has a lot of silica and maybe some other minerals dissolved in it. As minerals slowly precipitate out of the solution, the crystals grow by adding that material layer by layer to their outside edges and surfaces. This often does not happen at even rates or distribution. Pits, ridges, dents, and other imperfections can form on a surface and then when the next layer of material is added it can create a sealed cavity inside the crystal, trapping a bit of that original solution and creating a fluid inclusion!
That’s not the end of the story though. As the crystal and liquid trapped inside cool and contract, the liquid shrinks at a greater rate, allowing a little gas bubble to form inside the cavity as well. From an aesthetic point of view, fluid inclusions wouldn’t be quite as neat without that little bubble moving around - but they are useful scientifically too! If you want to know what conditions that crystal formed in, all you need to do is heat it up until the vapor is reabsorbed and you’ll have the temperature at which it grew. Perhaps you want to extract that liquid and gas and do some cool tests and find out all sorts of interesting things about what the earth and atmosphere were like millions of years ago. Or maybe you just want a beautiful little piece of deep time to wear and to wonder at and to help you start nerdy-cool conversations :)
trapped petroleum gives this fluid inclusion a bold yellow // geologyin.com
Fluid inclusions are found in many minerals but most are microscopically small. In fact, milky quartz is “milky” because it contains so many teeny tiny bubbles of liquid. It is less common to find fluid inclusion that can be seen with the naked eye.
a nice cluster of milky quartz from fossilera.com
If you’ve ever been shopping for diamonds you might think of inclusions as a bad word, a lot of value is placed on stones with high clarity. They can be quite beautiful, but in my world inclusions are a good thing.
dendritic agate // lodolite// rutilated quartz
The beautiful branching patterns in dendritic agate….INCLUSIONS!
The gorgeous “gardens” in lodolite…………...............INCLUSIONS!
Those crazy clusters of needles in rutilated quartz......INCLUSIONS!
I look forward to exploring all different types in future posts, but for now I will leave you with one more fun fact about fluid inclusions. In some cases, it’s not just gas and liquid that are contained inside the cavity, if there was a high enough concentration of minerals in the original solution, a tiny crystal may precipitate out of the liquid. A crystal in a crystal!!
As always, thanks for reading :)
Maranda
*Enhydros, or enhydro agates, are basically geodes that still have fluid inside. One of the main differences is that enhydros are permeable and fluid inclusions are not. And the difference between a regular geode and an enhydro is that the fluid that was once inside the geode allowing the crystals to form inside it’s cavity has slowly seeped out.
So now I am wondering...could a crystal with a fluid inclusion grow inside an enhydro geode? An enhydro within an enhydro?? Probably, right?! I’m going to hypothesize that yes, definitely that can and does happen!** But you would only be able to tell if you cut open the enhydro, which would let the fluid out and then it wouldn’t be an enhydro anymore….Schrodinger’s Enhydro?! Ok, thanks for coming along on that weird little journey with me, lol!
**If you are a person who knows about these things and wants to tell me how wrong (or right?) I got that - please do! But no thanks if you want to tell me that I got the Schrodinger’s Cat bit wrong, just try and enjoy my bad jokes :)