where ever you find geodudes one could be shiny i found a shiny before my first gym it was in Oreburgh Gate on Pearl
A gold geodude is just a shiny geodude you must keep finding geodude in granite cave until its shiny.
Anywhere you can find geodudes, but they are extremily rare.
Yes, any Pokemon can be shiny when it can be hatched from an Egg, including Geodude.
What you have encountered is a shiny Geodude, which, as you described, is gold and a normal Geodude is a light gray color. Think of shiny Geodude as a gold nugget and a normal Geodude has a regular rock.
You can't
As many as you can find I had a Sneasel Magikarp Geodude Shaymin and Seaking
You could just go to challenges and win to get a shiny geodude!
5234: Shiny Pidgey 5231: Shiny Geodude (once) 5231(space): Shiny geodude as many times as you want Shiny pikachu 0.05% chance of it appearing on veredant forest 1 or 2
If you mean a Shiny Geodude, they appear randomly and very rarely and there's no specific way to get it.
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You can find a Geodude in Route 206, 207, 210, 211, 214, 155, Lake Valor, Mt. Coronet, Oreburgh Gate, Iron Island, Ruins Maniac Cave, and in Stark Mountain.
5234- Shiny Pidgey 5231- Shiny Geodude 673034- Shiny Jigglypuff