Bi disc without decorations or inscription

the diameter is 21 cm and about 1 cm thick. The disc where not crusted has a green tone and with no polished surface remaining, if it ever was polished, it’s beyond me to say jade beyond tossing out Bi.

Ideas about authenticity?

 

Not all discs are jade....& this one doesn't have the look....to me ...

 

Ancient Bi discs are very rare.
Ancient jades do not look like modern jades, they are often much duller in colour. They tend to have a soft sheen.
This one could be jade, but the question is, how old. That is a question no one can answer from pictures. You will need an expert to look at it in person, and maybe analyze the stone and the carving marks.
The rounded sides make me think this is a later Bi/replica, but I am no expert on early jades. The rough pitting is a bit strange.
One of the things that is often looked for is shimmering bits in the stone. Those bits are mica extrusions which appear on the surface of jade after centuries of exposure to certain soils/conditions. I have an authenticated Liangzhu carving from an old collection that has that. I'll see if I can take a photo of it.
Mica can also appear on non-Neolithic pieces, it is on one of my antique jade snuff bottle as well.

 

Here are some photos, the mica extrusions are very difficult to capture. They mainly show as white spots, but when you move the piece around they reflect the light.
The Liangzhu carving, 3400–2250 BC, probably of the head of a deity:


It is often called Great Spirit, but of course little is known of this culture. It is 12 cm at the widest point.
Mica extrusions in the centre of the picture:


Mica extrusions against the upper left of left eye circle and above the ridge between the eyes:


The side, straight, no curves or rough pitting. Slightly rounded edges, soft sheen of the jade.

 

Found a video on ancient jade Bi discs and what is involved in authentication:

 

Thank you ANY. A very informative video, art exists for didactic purposes.

 

wonderful information and video

A closer look found this seeming inscription- see new images

 

Looks like it could be a proper engraving. On which part of the disc is it?