All About Geodes and How They Are Formed

as I'm sure you know there are plenty of

beautiful gemstones out there of varying

shapes and sizes but there's one

category of stones that teaches us it's

what's on the inside that counts the

geode if you're a rock nerd like me your

fascination with geology and gemology

probably began with geodes and of course

you are and of course it did an

unassuming stone with a hidden surprise


they're basically nature's wonder ball

but instead of mediocre candy you'll

find quartz crystals agate in some rare

cases opal but these amazing hidden gems

don't just form overnight it can

actually take these glittery micro

chasms thousands even millions of years

to form it all begins with the creation

of a cavity within a rock formation and

there are a few ways that can occur the

most common way these spaces are formed

is not by excessive consumption of candy

but by the water vapor and carbon

dioxide that gets trapped inside streams

of lava and magma since the co2 and

water vapor are both gaseous they create

spaces inside the molten block that gets

trapped as it cools these spaces also

form an underwater volcanic eruptions

the immediate contact between the ocean

water and the super hot lava causing

outside layers of magma to pull much

faster than the inside layers the

resulting pressure of the quickly cooled

outside layer on the molten inside layer

of the rock causes ruptures where the

molten rock can leak out leaving behind

an empty shell of now solid igneous rock

a third and less violent way these

spaces can occurs within sedimentary

rock over an extreme time layers of

sediment are packed on top of each other

but not all the organic materials swept

up in this process will turn into

sedimentary rock occasionally pieces of

wood coral and other minerals can get

trapped in the mix and may wither away

after the sedimentary rock is formed

around it leaving behind a cozy little

spot for crystals to grow in all these

cases the resulting cavity may appear to

be encased in a completely solid stone

but the outer shell is actually porous

on a microscopic level allowing

groundwater or rain water to seep into

the rock bringing a whole host of

minerals along for the ride the water is

just passing through but it leaves

behind these minerals that over time

begin to line the inner walls of the

cavity as these minerals settle down

they begin to stretch their proverbial

legs and form all kinds of crystal

shapes now the formation inside the

cavity varies depending on the type of

rock for instance you're more likely to

find the quartz crystals inside of

igneous overall can akak and silica is

more likely to form within a sedimentary


but homology laymen and laywomen out

there mostly associate us with quartz

crystals of either the milky or a

translucent variety or the deep purple

amethyst the two have the exact same

molecular structure but the iron

impurities in the amethyst give it an

amazing purple color that would have

certainly made Prince swoon she were

kind you find a secondhand store

amethyst has been unearthed all over the

world but the finest quality amethyst is

found in Brazil Siberia Mexico and the


and some of the largest geodes ever

discovered are amethyst and even agate

geodes can contain amethyst crystals now

I'm sure you've noticed me throwing out

the word agate a few times in this video

and you may be wondering what I'm

talking about the difference is in the

crystal structure these layers of agate

chalcedony create bands with different

impurities within the geode resulting in

multiple bands that look similar to the

sedimentary rock we were discussing

earlier the difference here is each band

contains a micro crystalline structure

now you may be wondering about the

difference between a geode and thunder

egg both form in similar ways with

similar internal crystals but the main

difference is in the formation as we

discussed Geo's are formed from mineral

deposits that coati inside of a cavity

and form in layers while a thunder egg

formed from silicon dioxide layers that

don't necessarily originate from the

perimeter of the cavity did you happen

to form from mineral deposits seeping

into a porous rock cavity formed by co2

gas trapped inside molten rock I didn't

but hey let us know in the comments and

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