A gazelem is “a stone, which shall shine forth in darkness unto light” (Alma 17:55 RAV, 37:23 OPV). It appears to be a type of or another name for a seer stone, as Alma states the stone will allow the user to see secret works, works of darkness, and wickedness and abominations. This is likely an ancient term for a seer stone.
Joseph Smith used the name Gazelam (with an “a”) as one of his code names in certain Sections of the Doctrine and Covenants for the Church of Latter Day Saints. This name was likely based on this stone.
See 4 Moses 30:9, 33:10, 41:6-12; Alma 17:55 RAV, 37:23 OPV; Doctrines of the Saints 43:6, 47:12. See also Seer stone.