n. A mixed chloride and borate of magnesium that occurs as a white to green crystalline evaporite, with the chemical formula Mg3B7O13Cl.
the GNU version of the Collaborative International Dictionary of English
n. A mineral of a white or gray color occurring massive and in isometric crystals; in composition it is a magnesium borate with magnesium chloride.
The Century Dictionary and Cyclopedia
n. A mineral consisting of borate and chlorid of magnesium.
Word Usage
"The principal boron minerals are borax or "tincal" (hydrated sodium borate), colemanite (hydrated calcium borate), ulexite (hydrated calcium-sodium borate), and boracite (magnesium chloro-borate)."