Frackers are expected to use nearly 95 billion pounds of sand this year. A sand mine in Garnavillo, Iowa. Stephen Mally for The Wall Street Journal Sand prices are rising and companies are racing to build new mines in South Dakota and other locations as demand intensifies for the silica crystals that energy companies use to frack oil and gas wells. Sand is a key ingredient in items from solar panels to smartphones, but in recent years billions of pounds of it have been poured down wells to help coax more fuel out of the ground. In hydraulic fracturing, sand is mixed in a slurry of water and chemicals, then pumped down a hole to crack open dense rocks so oil and gas can escape to the surface. Frackers are expected to use nearly 95 billion pounds of sand this year, up nearly 30% from 2013 and up 50% […]