Seems to have been developed sometime between 1977 and 1980, perhaps as early as 1976. 1977 has been temporarily added as a date here, in order to flag the game up as a very early example.
See Jason Dyer's All the Adventures project for a thorough exploration of the game, which also includes comments for a contemporary player of the game.
The C source code for Crystal Cave adventure, converted from the original Fortran by Kevin O'Gorman, ported to Linux and packaged by Glenn Hutchings is available on the IFarchive; as is a Macintosh version.
The Macintosh version of the game is playable online, but does include a minor bug near the start.
[+] Users who have solved this game
[+] Users currently playing this game
This appears buggy. I have tried to download the .sit file from https://www.macintoshrepository.org/6422-crystal-cave-adventure but Stuffit detects an error when attempting to expand the file. You end up with a 4kb read me file and an empty file with no extension.
I can expand it with Stuffit Expander 5.5 under Basilisk II, but Stuffit Expander 4.0.1 under Mini vMac doesn't want to know.
Thanks I'll give it a go. It sounds like you had the same issues as me.
I finally got it to run using Jason Dyer's HD image and downloading Basilisk II. It works ok using OS8.0 and the proforma ROM.