First of all, bluegrass square
Blue grass squares should be the rarest in MC, and this kind of squares will only appear in the grass. Imagine how big a project it is to find a blue square in a big green square. But many players are willing to look for this blue grass square, thus posing various shapes.
Second, the sponge box
This kind of box is only available in the marine monument, but it is often missed if you don't pay attention. In addition, the marine monument itself is relatively rare, so it is still relatively difficult to obtain. However, some players said that every marine monument will produce a sponge cube. So, if you find the marine monument, you must look for it in the past, maybe you will have a chance to see it.
Third, the Emerald Cube
This Rubik's Cube is the rarest mineral Rubik's Cube, and there are two ways to obtain it. The first is to obtain in a specific biota, and the second is to trade. Although this kind of box has a general effect, the people who own it are all bosses, so it is also a symbol of status.
These three kinds should be the rarest squares in MC. Although other squares are hard to see, the way to get them is relatively simple, and you can get them as long as you are willing to spend time and energy. Therefore, it does not belong to the category of rare squares that are difficult to obtain. I also want to remind you here, don't force the blue grass cube, keep it when you meet it, and forget it if you don't meet it.