Carnelian – Sobek is said to have a Temple of Carnelian on the mountain of Bakhu, on which the sky rests, situated in the East [Spell 108 Book of the Dead, Spell 160 Coffin Texts]. The East is the sunrise, and carnelian is often associated with the Sun in general, as well as the solar eyes, the horizon (including sunset), and lions. To be ‘carnelian-eyed’ was to become angry and dangerous. (1)
Obsidian – This association entirely comes from Sobek as Sobek-Geb-Kronos during the Ptolemaic Period. Obsidian was the sacred stone, or property, of Kronos and gods who were identified as him – according to Porphyry, black stones represented ‘unseen gods’. During this period, Sobek was often shown with the iconography of Kronos, and there are many obsidian gemstones on which Kronos was represented with a crocodile, or crocodile-headed male figure.
(1) Hussein, Angela Murock. 2010. Beware of the Red-Eyed Horus: The Significance of Carnelian in Egyptian Royal Jewelry.