I took the game's rocks from Build Mode and coloured them up.
There are 16 sparkling colours for each of the 5 rocks.
I called them Alien due to the multitude of different colour options.
You'll find them in Build Mode/Trees/Rocks. Their cost, unchanged from the originals, is as follows:
Apprentice Alien Rock.......450 Simoleons
Alien Rock of Wonder........145 Simoleons
Alien Stone of Versatility....90 Simoleons
Hipster Alien Rock Duo......60 Simoleons
Silent Sentinel Alien Rock..245 Simoleons
Remember, you can make these rocks, and many other decorations,
bigger on your lots by using Ctrl + ] and resize them down using Ctrl + [
