Concretions/geodes/rocks

[Northern Sharks]

Without getting too ultra technical, is there a way to decipher what may be a concretion,geode or regular rock based on natural appearance?

[Guest N.AL.hunter]

I do not think there is an accurate way to determine them. Some geodes will be very light weight for their size indicating the hollowness in them. But, some geodes I have found are almost completely filled with crystal and very heavy. I also tend to notice that geodes have a unique 'bumpy texture' to them, but some do not. So in my opinion, you just can't tell with any accuracy.

[ebrocklds]

i think the easiest ans most accurate way is to just smash a few open. this only works if you are at a site with several of them.

Brock

[Guest solius symbiosus]

All geodes have a chalcedony rind with secondary, or more, growths of crystals inside the rind.

[RJB]

Geodes, are usaully lumpy bumpy to some degree and come in all sizes and come from igneous rock and concretions are usually sorta smooth and come from some kind of sedimentary rock, sandstone, siltstone, limestone, mudstone or a combination of those and sometimes have fossils in them, and all other rocks are just rocks? Thats my take on it anyways. Not sure if that helps, but thar ya go.

RB

[Rain1950]

Don't confuse a geode with a thunderegg. Geodes are varying shape, thin skinned and filled with crystals. If there are layers of agate inside the rind, then it's a t-egg. Also a T-egg will normally have an outer shell of rhyolite

Concretions are normally made of softer materals than geodes or t-eggs, the colors will reflect it's host material in color. A rock, or stone normally will look different than the host material, and at most times will be made up of several different minerals

[Guest solius symbiosus]

Too, geodes are rather common in sedimentary rocks. I've only seen them from limestones, but they probably form in other seds