The pyrites is subjected to dry distillation from out of iron or fire-clay tubular retorts at a bright red heat.
Parkersburg is the see of a Protestant Episcopal bishop. Oil, coal, natural gas and fire-clay abound in the neighbouring region, and the city is engaged in the refining of oil and the manufacture of pottery, brick and tile, glass, lumber, furniture, flour, steel, and foundry and machine-shop products.
In connexion with the Warora colliery there is a fire-clay business.
Pittston is in the midst of the richest anthracite coal region of the state, and fire-clay also abounds in the vicinity.
The bed of fire-clay under a coal seam, being impervious to water, frequently determines the horizon of numerous springs issuing from the hillsides.
