I'll carve the text in the granite for you, no you do it.

Good points by Steve Shives thanks
Archaeologist Israel Finkelstein in his book,"The Bible unearthed" doubts that a large exodus of Israelites ever crossed the Sinai Peninsula as the evidence that should be there has never been found.
I think the stories may be mythical; made up.
In any case I think if something like it had happened then the Israelites would have told Moses that  the 10 commandments were nothing new as they already knew similar ideas from the 42 negative confessions on the Ancient Egyptian Papyrus of Ani.

Also how come Moses didn't complain, "God damn you, how the f'ing sheol is it that you had me walk past the limestone hills of Northern Sinai peninsula, and then walk past the Sandstone hills of middle Sinai and its only now that I am on the hardest granite mountain  you remember about carving tablets of stone ?"

So then God replies in Exodus 34v1,"I will write on the tablets of stone" but like the  boss from hell, Exodus 34v27"The Lord said to Moses,"Write down these words..."

Also interesting that the tablets of stone have gone missing, disappeared without a trace and the Bible nowhere mentions it - totally forgotten about, as if they never existed.

Note on the Geology of Sinai by F.W.Holland says
The peninsula of Sinai may be divided into three geological districts, named from the granitic, limestone, and sandstone rocks of which they are composed.
The whole of the northern portion of the peninsula is occupied by an extensive plateau of limestone,
A broad belt of sand, called the Debbet-er-Ramleh, separates this limestone from the southern Granite portion of the peninsula
http://jgslegacy.lyellcollection.org/content/22/1-2/491

Wikipedia says:
Mount Sinai's rocks were formed in the late stage of the Arabian-Nubian Shield's (ANS) evolution. Mount Sinai displays a ring complex  that consists of alkaline granites intruded into diverse rock types, including volcanics.