(Min.) A hydrous carbonate of magnesia occurring in white, earthy, amorphous masses.
hydromagnesite
hydromagnesite
[‚hī·drō′mag·nə‚zīt] (mineralogy) Mg4(OH)2(CO3)3·3H2O A white, earthy mineral crystallizing in the monoclinic system and found in small crystals, amorphous masses, or chalky crusts.