Tiffany Stone:    The origins and formation of it silica compositions

 

So how did the silica-rich layers and Tiffany stone nodules occur then? Some are made of marble, Quartz or quartzite, and agate- Some are an opal-like chert with chalcedony breccia patterns-and some are all mixed up with it all.   Here are some explanations, and I will list them in order to how they took place. 

 

First, the Quartz, Quartzite, and some times harder cherts and agates: Some areas have more than others and is some what indicated by the content it has in the Tiffany Stone or in other rocks close by.  Fine quartz sand or particles- from erosion of near-by quartz deposits and mostly from devitrified silica rich volcanic ash in the water from first-stage volcanic activity- settled at variable concentrations along the semi-solid limestone floor where the up-most layers would have been more like mud than rock.  The limestone had other interesting mineral deposits in close relation with it- including manganese oxide, which causes those sometimes metallic looking black colors in Tiffany Stone. (Manganese and its oxidizing may have also been in the volcanic ash and it is not entirely clear which one to credit it to- if not both).  There were then two ways that this layer solidified into rock: one is that they formed prior to the larger eruption(s) taking a long while to form -perhaps millions of years. The second way, which seems the more likely, Is that this silica rich layer was not there very long -being still an oozy mud or semi-hardened rock- when the much larger second-stage eruptions of hot volcanic ash, (along with rhyolite overburden that later covered the ash body) covered these sediments. This would have then contributed to some metamorphic change (heat and pressure) where eventually the courser gained quartz turned into quartzite and the finer, often devitrified (similar to dissolved, but not so completely) types, turned into fine crystalline agates, jasper, and cherts (types of chalcedony).  Being covered by immense weight and heat, these chalcedony formations would all have formed at a highly accelerated rate.  Most of the Tiffany Stone has its silica quartz types coming from this geological event, though not all- especially the amorphous (none crystalline) opalites.  The opalite formed a little later after the huge volcanic eruption of ash from the Thomas Range .   

 

 In the interim of volcanic activity came geothermal fluorine gases from deeper down in the Earth which penetrated both volcanic ash and siliceous sediment after making its way up through week spots in the limestone floor.  Looking closely at a few pieces of Tiffany Stone can tell us a lot about where the fluorine got itself first. If fluorine was saturated in the silica prior to the volcanic eruption- or deeper down where the ash did not effect it as much- then it has a gemmy and some times semi-translucent appearance and the material is often more solid and stable. If the fluorine was saturated in the volcanic ash prior to the nodules solidifying, then it often has a creamy opaque texture and some tend to be of slightly softer and/or less stable- being mostly made out of opalite. Still, the opalite varieties can be good and hard but vary depending on its volcanic ash content, as well as if it got intermixed with the original silica rich layers. More ash (not enough solidification of the ash) means it is mostly going to be unstable and easy to break and fall apart.  Think of powdered sugar as the volcanic ash. If you got it wet and dissolved it and let it dry out, it would crystallize and be harder, but if you left it only slightly damp and dried it, it would not hold together very well being rather crumbly and powder-like.     Opalite is amorphous, meaning it has no crystalline structure and is not technically a mineral, and there are two common ways silica of a glassy nature of this sort can form. Some may be familiar that obsidian is amorphous volcanic glass and forms through the melting and re-solidification of volcanic ash. And while some tiffany nodules may have formed through a similar process, most of it formed through the devitrifying of the volcanic ash in water (similar to dissolving, but not so completely).  This formed the amorphous “hydro-silicate” types commonly associated with opals. The body of ash spewed pretty much into a sea of water and settled on the bottom, but like taking a large scoop of sugar and suddenly dumpling it into an inch deep bowl of water, what happens? It does not all get wet very fast and much of it stays dry.  The silica volcanic ash does not dissolve near as quickly as sugar, but the concept is the same.  Hot temperatures of the ash may have helped speed up the devitrification process.    Those areas of ash underneath the water, or where water got churned into the ash, eventually became devitrified and formed layers or nodules of tiffany stone when they slowly dried out. All this is similar to how “opalite” forms in Tiffany Stone; however, Tiffany Stone is not always amorphous like other opals as it all depends on its formation qualities and conditions. When it is in a mid-way state like this we call it semi-opalized and it is perhaps more correct to call it a kind of chalcedony and put it into the mineral status.  It is note-worthy as well that because Tiffany Stone is composed of so many other minerals, it would have formed variable crystalline structures within the opalites, making the majority to be less likely to be without some sort of crystalline structure.  Tiffany Stone, after all, is a mix of many different minerals and elements in one, and seemingly, it may have some amorphous solids right next to some crystalline solids too.  

 

A little side note:   In many instances the water may have also been mixed with fragments or parts of the older chalcedony and marble (metamorphosed lime stone) moving around as the water in this area was probably violently boiling in many areas- especially around the hot fluorine gas vents.  This would explain why we sometimes find “foreign” material in some tiffany stone. Another possibility is that former chalcedony deposits located nearer the volcanic eruption got broken apart and thrown at random into the forceful body of ash, probably moving at hundreds of miles per hour.      

 

Now how about those brecciated patterns that hold together the broken up bits of the older silica rocks, limestone, or solidified ash? Well, these are areas where devitrifying or complete dissolving of the silica-rich ash occurred and the water (you can think of “ground water”) carried it down into all the voids and cracks of the ash and broken up rocks underneath.

This also helps to explain why the “healed crack” breccias are crystalline solids and not amorphous because to form amorphously the way hydro-silicate opal and opalites do, it needs to have an undisturbed and still environment of settling, otherwise the water gets worked out. In this case, the water and silica seems to have settled down straight through and did not sit anywhere very long, but just right to leave whatever it reached to be fantastically re-solidified. Also, the way the nodules cooled (if gases pockets), or dried out (if by water solutions), it left behind fantastic quartz druzzies or geode pockets!