A key member of Van Halen's early days has died. Mark Stone, (seen far left in the above photo) who played in the pre-Van Halen groups Genesis and Mammoth, died Saturday (Sept. 26) according to the musician's brother.

Brad Stone kept his message brief on Instagram, stating, "My beloved brother Mark passed this morning. #markstone #vanhalen #fanhalen."

After the Van Halen brothers' previous bassist moved away, Mark Stone joined the group, forming a trio with Eddie also singing. They would later add David Lee Roth to handle vocals, making the group a foursome. "I went to jam. They just called and said come over and jam and let's see what happens," recalled Stone in The Van Halen Story: The Early Years documentary. "I knew early on that they were both virtuosos. There were few legendary guitar players and I knew Edward was on his way to being there. Alex was the leader. He was the driving force that gave the band direction."

Stone was with the band between 1972-1974, but was later replaced by Michael Anthony. He did appear on the demos for the tracks "Glitter," "Gentlemen of Leisure," "Angel Eyes" and "Believe Me."

In The Van Halen Story: The Early Years documentary, it was revealed that Stone was split between his education and being in the band, with the group eventually asking him to leave as his "interests lied elsewhere." "I just couldn't keep up with them," stated Stone, who admitted he knew they were meant for bigger things.

In his later years, Stone would keep up the Van Halen association, making guest appearances with the tribute band Fan Halen.

Van Halen, "Gentlemen of Leisure" (1973 demo)

Mark Stone Plays With Fan Halen

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