The Story of a Monument

Part 1

The story of a monument begins with the story of Dakota Mahogany granite. According to the US Geological Service, who determines rock ages by radioactive decay, Dakota Mahogany is approximately 3.5 billion years old. In more recent times, the glacier came across the Minnesota River Valley and with tremendous force, removed the overburden from the now cooled rock, revealing outcroppings of solid granite. Being poor farm land, the outcroppings were largely ignored until 1917 when Alex Dewar, one of our founders, started to quarry it for monumental use. The granite layer in our area is said to be between 5 and 15 miles thick and its color is quite vertically consistent. In mineral makeup, Dakota Mahogany is considered a high quartz granite at about 33%. Quartz is the hardest material in our granite and is chemically similar to amethyst and other semi-precious stones. The other major component of Dakota Mahogany is a family of feldspars which are silicates and only slightly softer than the quartz. It is the feldspars which give granite its color as they contaminate with various metallic oxides. For example, aluminum oxide will tend to give the feldspars a bluish phase while iron will lend a reddish character.

In the earlier years, quarries always began with outcroppings since means of earth removal was primitive at best. In more recent times, exploration by soundings would indicate buried ledges that could be uncovered by modern earth moving equipment. Exact color of buried granite is always a guess at best. Most "discoveries" are verified by drilling off a smaller piece of the ledge and polishing it before further expenditures are made. Environmental concerns with our land have mandated reclamation plans that are costly and very time consuming to implement. This is why, in South Dakota at least, most quarriers tend to enlarge present quarries rather than to search for new deposits.

In the next part we will explore actual quarrying and the equipment and procedures necessary for the job.