· KATY, Texas, Dec. 3, 2019 /PRNewswire/ Silica Holdings, Inc. (NYSE: SLCA) said today that part of its Industrial and Specialty Products business will increase prices for most of its noncontracted silica sand, aggregate diatomaceous earth and clay products used primarily in foundry, paints, coatings, elastomers, roofing, chemicals, recreation, building products, agricultural, pet ...