The Xorn is a Medium Earth Elemental that has the unique state of being Neutral and also haviong the ability: Treasure Sense

"Treasure Sense. The xorn can pinpoint, by scent, the location of precious metals and stones, such as coins and gems, within 60 feet of it."

If you take this ability into account, you can create a money farm by using Conjure Elemental and Planar Binding to order the Xorn to search and bring back diamonds and other precious gems that it finds in the area to you. It can do this because of the ability Earth Glide.

"Earth Glide. The xorn can burrow through nonmagical, unworked earth and stone. While doing so, the xorn doesn't disturb the material it moves through."

My question is: How much (worth of GP) gems could the Xorn find on average each day? 

I've heard that it will always find more that 1000gp worth of jems each day, but I think that it would be much higher that that.

I have attached a google sheets file to this post so you can determine the amout of gemstones that I belive the Xorn would find each hour: https://docs.google.com/spreadsheets/d/1ww5lNtBNjQN3D7svXZ-BpRLqb6iwIXe8kse3sOV04Ho/edit?gid=0#gid=0

That being said, normaly the Xorn don't drop loot becasue they would normaly digest any gemstones they find. I belive that the Xorn should (if killed in the wild) drop two of the gemstones that I listed in the above table.

Would it not be easier to Polymorph into a Xorn?

edit: whups, can only do beasts. forgot.

If DND were a game that focused on how to micro manage and make the most money possible, then this would be a great idea. But honestly, there are plenty of ways to "break" the system and get loads of money using magic - they're just generally not done out of mutual understanding of the game etiquette. Things like Fabricate to make Platemail and sell it every day, etc. 

However, DND is a game focused on adventuring, intrigue, and fighting monsters. This is a cool idea, but would most likely get a few eye rolls if it were used at my table, personally. 

Well whatever floats your boat right?

Quote from NagolTheNaySayer >>

My question is: How much (worth of GP) gems could the Xorn find on average each day? 

I've heard that it will always find more that 1000gp worth of jems each day, but I think that it would be much higher that that.

 Things to consider:

• Are you in an area where diamonds can even be found?
  • The ground all around you isn't littered with diamonds. The ground in a lot of places isn't. Below is a map of the world you live in and where people tend to actually be able to mine for diamonds. You may notice large swaths of land that doesn't happen. So beyond summoning a Xorn and binding it to your will, you would also probably need to find a piece of land that actually has gems to mine that also doesn't happen to be claimed by other folk like a mining company or some local lord or city that might not take kindly to you stealing their resources with your pet monster.
  • 
• Xorns are intelligent creatures and probably do not take kindly to folks who summon and then try to enslave them. The Planar Binding spell only lasts for 24 hours at the normal casting and hostile creatures will not efficiently do tasks assigned. Assuming you instead befriend the Xorn, it will probably attempt to find precious gems and metals for you, but will likely eat some of them as well. Also it will probably want to take breaks as trudging around all day under ground sensing for and delivering treasures is probably tiring.
• You are no the first person to have this idea. This is actually a plot of more than one published adventure from previous editions and often the perpetrators are seen as villains that the party has to deal with and free the enslaved Xorn or cleared out by request of local authorities for resource stealing.