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Solfe
2015-Jun-14, 02:29 AM
Are there any natural processes like lightning or volcanic events that form either spherical or oblong shaped pieces of glass?

Another question is, are there ever fragments or crystals of naturally occurring glass that are mostly uncolored?

The third question is, do natural processes ever form glass that would be large and flat enough for windows?

I tried wikipedia, but my light browsing only resulted in materials that are very, very rough and often not clear at all.

The reason for this question is, I seem to recall a story where people obtained glass for window panes from natural sources. I believe that the source was lightning strikes and it was extremely distorted and not entirely transparent. I can't remember if this was a history book or something else. I could even be mis-remembering entirely.

swampyankee
2015-Jun-14, 03:41 AM
Obsidian is a natural glass. There are naturally occurring quartz crystals (clearly, these are not glass) large enough make into windows if -- and this is an incredibly large "if" -- they can be sliced into pieces thin enough to see through.

grapes
2015-Jun-14, 03:52 AM
Large sheets of mica were used for heat-resistant windows into stoves even long after glass manufacturing. Lightning strikes in sand produce natural glass, it couldn't have been long before some genius fired up their own though.

geonuc
2015-Jun-14, 11:17 AM
Are there any natural processes like lightning or volcanic events that form either spherical or oblong shaped pieces of glass?

Yes. Some eruptions are obsidian in nature and if the volcano spat out material, you'll find lots of spherical or near-spherical obsidian pebbles, or nodules, laying about. An example is Glass Mountain in California.

grapes
2015-Jun-14, 12:02 PM
Interesting. The wiki on fulgurites ( https://en.m.wikipedia.org/wiki/Fulgurite ) says that Yale has the longest preserved fulgurite, of length 4 meters, but Darwin on his voyage noted ones of 9 meters length.

Squink
2015-Jun-14, 12:53 PM
Do tektites (https://www.google.com/search?q=tektites&source=lnms&tbm=isch&sa=X&ved=0CAkQ_AUoA2oVChMIssm1g52PxgIV0Q6SCh25JwCw&biw=1003&bih=511) count?

cjameshuff
2015-Jun-14, 01:04 PM
Obsidian-producing lava could potentially form sheets, but I doubt any volcano has consistently produced glass in a form suitable for windows. Lightning strikes don't form anything suitable as window panes.

The only natural geological source for window "glass" I can think of is mica, which is sometimes called isinglass (a term also used for a completely different substance produced from the swim bladders of fish). It's not a glass (it's a crystalline mineral) and has nothing to do with lightning, but the author may have simply been mistaken.

NEOWatcher
2015-Jun-14, 02:32 PM
(clearly, these are not glass)
:lol:

Solfe
2015-Jun-14, 02:56 PM
Humm... and my next thread will be on "Faulty Memory". :)

All of this is actually very helpful despite the fact that my memory is shot.

The purpose for this inquiry is I am writing a D&D campaign with an unusual history, the people of one tribal kingdom "worship" planets. I was hoping that a natural glass would have lead to the idea of having ground lenses as a common item for the cheap production of telescopes. I think I can contrive a series of events where people endeavor to be expert glassworkers as a result of observations of the natural world, which would lead to telescopes.

I drew this funny temple, with four circular "decks" where telescopes and astronomical information is stored for Venus, Mars, Jupiter and Saturn. Between the decks are thee cave like structures, one for the moon, the sea and "the fires", which is their term for Mercury and the stars. They already the Copernican Theory which all of their neighbors distrust. They are well known for "curing the eyes" with "magical" devices.

Thank you for the information. I am sure I can build a narrative structure where the raw materials and natural observations can lead to glass lenses. The idea of having worked minerals sort of enhances the mystique of this tribe.

cjameshuff
2015-Jun-14, 03:25 PM
Humm... and my next thread will be on "Faulty Memory". :)

All of this is actually very helpful despite the fact that my memory is shot.

The purpose for this inquiry is I am writing a D&D campaign with an unusual history, the people of one tribal kingdom "worship" planets. I was hoping that a natural glass would have lead to the idea of having ground lenses as a common item for the cheap production of telescopes. I think I can contrive a series of events where people endeavor to be expert glassworkers as a result of observations of the natural world, which would lead to telescopes.

I drew this funny temple, with four circular "decks" where telescopes and astronomical information is stored for Venus, Mars, Jupiter and Saturn. Between the decks are thee cave like structures, one for the moon, the sea and "the fires", which is their term for Mercury and the stars. They already the Copernican Theory which all of their neighbors distrust. They are well known for "curing the eyes" with "magical" devices.

Thank you for the information. I am sure I can build a narrative structure where the raw materials and natural observations can lead to glass lenses. The idea of having worked minerals sort of enhances the mystique of this tribe.

Glass for lenses is an entirely different matter than transparent window panes. Lenses need better clarity, but don't need large, flat, thin panes of uniform thickness.
If they don't have glass, appropriately shaped quartz crystal would substitute, look at the Nimrud and Visby lenses.

swampyankee
2015-Jun-14, 04:06 PM
Technologically produced glass has been around for a very long time. I don't know when the first glass was deliberately produced -- according to here (http://www.historyofglass.com/) it was in about 3500 BCE -- and getting clear glass was mostly a matter of purity of materials and minimizing bubbles and inclusions. Getting small chunks clear would be easier than getting clear sheets.

Solfe
2015-Jun-14, 11:12 PM
Glass for lenses is an entirely different matter than transparent window panes. Lenses need better clarity, but don't need large, flat, thin panes of uniform thickness.
If they don't have glass, appropriately shaped quartz crystal would substitute, look at the Nimrud and Visby lenses.

Really? That is perfect! Thank you for that information!

Noclevername
2015-Jun-15, 12:38 AM
Observing the effects of water drops on images is IIRC what first led to lenses being invented. The drops would probably be caught on spider webs or other relatively static structures.