Why are some roads red?

Ever notice that some roads are red?

The color is determined by the aggregate used to build them. Most roads are black or grey because most rock aggregate is black or grey. Rock from quarries like this one in Kemptown, Colchester County, gives roads a reddish color.

The Kemptown quarry’s granite looks red from a distance but up close it is actually a mixture of red, orange and grey. That is because it contains a high percentage of orthoclase feldspar which is red/orange in color.

Stone from the Kemptown quarry was also used in the rock garden at Dalhousie’s agricultural campus in Truro. The rock garden was built in 2002 and covers over half an acre. Six hundred tons of Kemptown granite were used to build it.

The rock garden and the others on the agricultural campus are tourist attractions. The rock garden also offers an opportunity for students to learn about unusual plants and how to create effective habitats in which to grow them.

Aggregate is the most-mined material in the world because it is used in virtually all infrastructure, including homes, roads, schools and hospitals. Aggregate makes up about 80% of concrete and 94% of asphalt.

Building one kilometre of highway takes about 18,000 tons of aggregate - enough rock to fill four Olympic-sized swimming pools! Nova Scotia needs 10-15 million tonnes of new aggregate each year to build and maintain our infrastructure.

Dalhousie Agricultural campus rock garden.

Kemptown Quarry.