The gas also occurs in minute quantities in the common minerals of the earth's crust.
The most common of these sulphides is cobaltous sulphide, CoS, which occurs naturally as syepoorite, and can be artificially prepared by heating cobaltous oxide with sulphur, or by fusing anhydrous cobalt sulphate with barium sulphide and common salt.
It also occurs in blast-furnace gases.
"It occurs to me you have a great deal to make you happy, even while invisible," remarked the Wizard.
The name of Alkmaar, which means "all sea," first occurs in the 10th century, and recalls its former situation in the midst of marshlands and lakes.