yes you can. you can find obsidian by digging down constantly. but I'm not to sure about missouri
You'll find obsidian by volcanoes where the magma cooled ultra-quickly.
Type in "buy obsidian" in your search bar. You will be given information on several sources. Knappable obsidian sells for around $5 US per pound.
Obsidian is usually found in caves underground where flowing water hits still lava.
Obsidian is a volcanic rock, so I'd assume most places with volcanoes.
You could find obsidian near a volcano.
Once you build the stone hammer you go to the Dark Cave and you will find obsidian deposits.
Any of the Lava Isles are where you can find obsidian chunks. There is no "best" place. Also, sometimes you can find them in the rock shops if another player has sold them recently.
Obsidian is molten silica (read sand) which has cooled rapidly after a volcanic eruption into brittle glass and is the reason why it chips easily into blades. Iron and magnesium give obsidian its dark color.
obsidian
you could find a pool of lave place water then it turnes the lava to obsidian to get it you have to mine it up with a pickaxe
make the nether reacter