Over a billion years ago, molten rock beneath Stearns County surged toward the earth's crust. As the rock cooled, the minerals in the rock condensed and hardened; forming deposits of very durable granite. Outcroppings of these Pre-Cambrian rocks are found in a 10 square mile area mainly between St. Cloud and Rockville. Colored granite deposits were discovered here in 1868, which gave the city it's nickname of "The Granite City."

These porphyritic igneous rocks are a true granite of Early Proterozoic age (1700-1800 million years ago). They are quarried near the town of St. Cloud Minnesota. The main minerals evident in the rock are quartz, potassium feldspar, plagioclase feldspar, and biotite. Smaller amounts of zircon, apatite, hornblende, chlorite sericite and sphene also occur. The potassium feldspars are the large crystals ("phenocrysts") set in an otherwise equi-granular matrix. The pink color of diamond pink is due to pink coloration in those particular rocks feldspars.

The first granite quarry opened in Minnesota was the Breen & Young quarry at East St. Cloud in Sherburne County in the spring of 1868. Their first order was to prepare stone for the corners and steps of the United States customhouse and post office in St. Paul. In the two years from the beginning of 1869 to 1871 the shipments of granite from St. Cloud to St. Paul amounted to 2,200 tons.

Granite quarry south of St. Cloud, 1890. MHS visual resources, HD6.2 p19

Early quarrying techniques made use of biological power. Men armed with hammers and chisels would painstakingly pound a row of holes into the rock. Dynamite was dropped into these holes to loosen the rock. The granite was then extracted on the backs of men and horses. Horse drawn wagons brought the granite to the rising cities of St. Paul and Minneapolis for building construction. Steamships on the Mississippi River distributed granite to the southern part of the country. Workers were constantly exposed to clouds of dust and smoke. As a result silicosis of the lungs was a common affliction of early miners.

All imperfect stone and waste rock had to be constantly cleared from the quarry. Scrap rockaccumulates rapidly and at all the quarries there are still great mountains of what is commonly called grout.

Granite quarry, St. Cloud, 1930. MHS visual resources, HD6.2 p45