"So Joseph died at the age of a hundred and ten. And after they embalmed him, he was placed in a coffin in Egypt.- Genesis 50:26"

Although it is true that Joseph was embalmed by the Egyptians, it is probable that he was not embalmed in their customary manner. They believed in preserving a body in order that it may be reunited with the soul, and this would have been against his religious beliefs.

Most likely they placed him in a sarcophagus, which is a stone coffin, often decorated, and located above ground. This is because he had given the instructions that the sons of Israel must "carry my bones up from this place" Gen.50:25

Note that Joseph did not request that his "body" be carried up, which would have been his probable condition had he been embalmed in the traditional Egyptian manner. It was his "bones" that were to leave Egypt. This denotes that he was going to be buried in a sarcophagus made of limestone.

The word sarcophagus is a gruesome name and is derived from Latin and Greek, coming from sarx (flesh) and phagein (to eat). The Greek word sarkophagos meant "eating flesh" and in the phrase "lithos (stone) sarcophagus" represented a limestone that was thought to decompose the flesh of corpses that were put into it.

After a while the Greek word sarkophagos used by itself came to mean "coffin"

When the term came into Latin then into English it at first referred to that same limestone. Then in 1705, it meant any stone coffin.

Considering that in Ex. 13:19 it is written that "Moses took the bones of Joseph with him," it's likely that Joseph's coffin was made of a limestone that consumed the flesh between the time of his burial and the time when his "bones" were taken by Moses.