[MayflowerMadam]

Not even close. It’s clear — really like lime Jello. About 15” in size.

(What even is that thing?)

[Red Badger]

https://en.wikipedia.org/wiki/Flint

[Red Badger]

Here’s some common green minerals:

https://kamayojewelry.com/gemstone-colors/green-gemstone-names/

[kiryandil]

Take a picture of your rock with your phone or a digital camera, and upload it to your computer.

Put the computer location of the picture into your Internet browser URL address line, and do a Goolag image search on the picture.

I've been doing that lately with unknown flowers. Works great.