When I was a boy, we practically lived on a 'rock pile.'  Perhaps to keep his five boys busy, my father had us pick up a lot of rocks around our home.  Digging post holes for fences was particularly challenging.  The farm I later worked on to earn money for college was also on a 'rock pile.'  Every time the cultivator or chisel was pulled over the ground, it seemed to pull up more rocks hidden under the surface.  Big rocks, little rocks, medium-sized rocks.  Some we picked up by hand, some we picked up by machine, some we blew to bits with dynamite... and some were so big they were left alone.
The purpose of this mod is to simulate the experience of digging up rocks during the tillage process.  The “rock spawn” mod is a global specialization that will affix itself to all plows and cultivators in-game.  If activated during tillage, rocks will occasionally be dug out of the ground.  The player may choose between 5 varying levels of rock spawn output, or to turn off the feature entirely, all from the comfortable seat of the tractor… which is a choice we didn’t have back in the day.  A few details pertaining to the mod are below.  The rest may be found in a pdf file manual included in the mod zip file, including instructions on how to customize the mod further if desired.
Input Binding:  ALT-R
Number of Rocks Included With Mod:  15 (small to large)
Multiplayer Ready:  Yes
Rock Spawning Levels:

The middle-left column is the approximate number of rocks that will spawn in the entire field # 16 on Westbridge for a particular setting.  The rightmost column shows the approximate number of rocks per hectare for each setting.  Each rock has an equal chance of spawning during the tillage process, with one exception: A “gold” rock is included in the pack.  The chance of it spawning during tillage is 1:1,401.  It may be sold for substantially more than regular rocks.
Rock FillTypes:  rock, gold
Two new fillTypes are registered with this mod – rock and gold – and their ‘sales’ value will fluctuate on the market like other fruits or fillTypes.  Each rock has different fillLevels, depending on their size.  Rocks may be disposed of at any bale destroyer trigger.
Note:
●  Each rock is a dynamic physics object, similar to a bale.  As such, it requires computing power in the game engine to render each rock and to remember where they are moved to.  The same recommendations and warnings regarding too many bales are also applicable to rocks. So... do pick up after yourself.

●  The stock game does not come with rock handling equipment, with exception of the loader buckets and forks.  The manual included with the mod contains a few suggestions as to mods you may wish to consider to help you pick up and deal with all the rocks you spawn.  Anyone using this mod is urged to review the manual, and consider additional mods needed before using this mod in-game.
Enjoy the rocks!