Deuteronomy 10:
Exodus 37:1
Wiki:
They wouldn't be too big for Moses to carry them up the mountain and smaller than the dimensions of the ark.1 At that time the Lord said to me, “Chisel out two stone tablets like the first ones and come up to me on the mountain. Also make a wooden ark. 2 I will write on the tablets the words that were on the first tablets, which you broke. Then you are to put them in the ark.”
Exodus 37:1
The ark was approximately 131×79×79 cm or 52×31×31 in.Bezalel made the ark of acacia wood--two and a half cubits long, a cubit and a half wide, and a cubit and a half high.
Wiki:
According to the Talmud, each Tablet was square, six Tefachim (approximately 50 centimeters, 20 inches) wide and high, and more a thicker block than a tablet, at three Tefachim (25 centimeters, 10 inches) thick
According to traditional teachings of Judaism in the Talmud, they were made of blue sapphire stone as a symbolic reminder of the sky, the heavens, and ultimately of God's throne. Many Torah scholars, however, have opined that the biblical sapir was, in fact, lapis lazuli (see Exodus 24:10, lapis lazuli is a possible alternate rendering of "sapphire" the stone pavement under God's feet when the intention to craft the tablets of the covenant is disclosed Exodus 24:12).