"In the middle-ages, the trope was a kind of musical commentary on sacred writings. The Sacred Stones is Jon Anderson's commentary on that moment within The Silmarillion when the Valar had brought Morgoth, the dark lord, to justice and recovered the most sacred of jewels, the Silmarils. While sacred, the stones where also cursed. They always brought madness and death to those who sought them. Even to name them was to awaken some hidden evil."
Update:
This is from the liner notes for the album.
"In the middle-ages, the trope was a kind of musical commentary on sacred writings. The Sacred Stones is Jon Anderson's commentary on that moment within The Silmarillion when the Valar had brought Morgoth, the dark lord, to justice and recovered the most sacred of jewels, the Silmarils. While sacred, the stones where also cursed. They always brought madness and death to those who sought them. Even to name them was to awaken some hidden evil."