What's the Name of That Book??? discussion

I read this back in the mid 70s in my school library...

After a storm, college students go to examine the cliffs to find minerals (or fossils) revealed by the storm. They observe something glimmering in a short cliff face. They find that it is a large crystalline box. With help from their college professor they get it back to the university and determine that it is a sarcophagus, and there's a being inside (reptilian).

Spoiler:
They manage to get it open and the being becomes reanimated.

Through a number of chapters, the students and professor become able to communicate with the being. Eventually the story takes us to where this being is from (under the ocean) and
they visit his home through use of a boring/tunneling machine.

Elements:
-Diamond: Lots of diamond tech in this story
-Boring machine tech: from the reptilian being's civilization
-Teaching tech: on board there's a machine that facilitated
communication between the species. Something about
diamond fibers penetrating their brains and communicating
directly at a neuron level

-decadent culture: they find the being's culture in horrid
decline. The civilization is tended to by fantastic machines
that have run hundreds, maybe thousands of years without
maintenance. One by one they fall offline. No one in the
current culture knows how to repair them

Further, the remains of this civilization are decadent, apathetic,
and lay about strung out on drugs.

Cover:
I can't be sure but I believe it had a reptilian man's face as the
sole topic of the cover.

Searched and searched for this book with no luck.

Thanks

Hello. Great description! Spot on in your notes. Easily recognizable.

This is Stranger from the Depths by Gerry Turner.

Looks like you've nailed it, thanks Brad! That did'nt take very long. :)

Glad to hear you were able to confirm. Kudos to you. Your detailed and very accurate description really helped in the identification. It has been a while since I last read it. But your description was immediately recognizable.