Stone had been under hospice care recently, according to Van Halen News Desk.
Stone played alongside drummer Alex Van Halen and guitarist Eddie Van Halen in pre-Van Halen bands named Genesis and Mammoth, and was a member of Van Halen from 1972 to 1974, when he was replaced by Michael Anthony.
His playing can be heard on unreleased demo tracks "Gentleman of Leisure," "Angel Eyes," "Glitter" and "Believe Me."
Stone was kicked out of the band because of his unwillingness to sing background vocals at a time they were heavily reliant on harmonies, as stated in the book "Van Halen Rising: How a Southern California Backyard Party Band Saved Heavy Metal"
I just don't want to sing by myself anymore.
According to Van Halen brothers' childhood friend Peter Burke, Mark Stone had great meter and sounded wonderful.
Stone says that attempting to divide his energy between schoolwork and Van Halen is what led to his departure from the group:
I was a straight A student, and doing the band. I was split between those two things, and basically I couldn't keep up. We met one day, and they actually asked me to leave. For a long time it was really tough. It was really tough leaving that band because I knew they were destined for greatness. They say, 'Don't leave before the miracle happens,' and I did.