laterite

This is a word I expect to have seen only in one instance and never see again, but words have a funny way of reappearing once you've really noticed them, so maybe I'm wrong about that. In a recent reading of A Good Man in Africa by William Boyd, "laterite" appeared not once but six times--I know because I used Google Books to find the different instances. Although it becomes clear that it's some sort of paving substance, it never really gets any clearer what that substance is.

"a well-trodden patch of laterite"

"a bald laterite square"

"the far end of the laterite compound"

"a rutted laterite track"

I suppose the one thing you can gather from this is that laterite is a commonly used substance, at least in the West African country that Boyd has invented to tell his story. But maybe we can learn a little more than that.

Wikipedia has an uncharacteristically "we throw up our hands" sort of comment about laterite:

Laterite has commonly been referred to as a soil type as well as being a rock type. This and further variation in the modes of conceptualizing about laterite (e.g. also as a complete weathering profile or theory about weathering) has led to calls for the term to be abandoned altogether. At least a few researchers specializing in regolith development have considered that hopeless confusion has evolved around the name. There is no likelihood, however, that the name will ever be abandoned; for material that looks highly similar to the Indian laterite occurs abundantly worldwide, and it is reasonable to call such material laterite.

More helpfully, though, they do agree that it is an iron oxide rich substance formed by long weathering of the parent rock. Laterite tends to be found in wet tropical places. 

About the origin of the word, however, things are a lot clearer. Again via Wikipedia, it was named by Francis Buchanan-Hamilton, a Scottish physician who after time spent in the Merchant Navy ended up in India. He seems to have been a man of diverse talents, as, in addition to becoming the surgeon to the Governor General of India, he also got together the Calcutta zoo. He was asked to do two very extensive surveys of regions in South India, which included reports on things as diverse as topography, antiquities and agriculture. In 1807 he named a rock formation he'd come upon laterite, taking later from the Latin for brick. (You can find a nice quote from him about lateite at a website called Z'shell-TeR .)There is even a monument to mark the spot where he defined it in Angadipuram, Kerala, India:

                                                    Werner Schellmann

For, although so far I've mentioned laterite as a paving surface, it is also quite commonly formed into bricks. Even Angkor Wat, the famous Cambodian temple known for its  beautiful sandstone relief work has an underlying structure of laterite. National Geographic has a nice short video explaining all this.

                                                    Werner Schellman

The usage I had more in mind,though, relates to laterite used as pavement in Africa.  The French used it a lot in their colonies, including their African ones. As William Boyd pointed out in his interview at The White Review, the part of West Africa where he grew up wasn't colonized, but the practice of using laterite for roads and the like must have spread to the region, since he uses the word so casually in his novel. An African road of laterite in Senegal looks like this:

                                                                         Dorothy Voorhees

Apparently, these roads work quite as well as gravel roads, but as there is clay in their composition they have a tendency to get slick when wet.

In Boyd's novel, I still am not sure what all the areas he mentions laterite in actually look like. The trails probably look a little like the picture above, but the laterite square could have been paved with bricks like this:

If it was made of laterite, though, it almost certainly would have been some sort of shade of rusty red.