The Nitty-Gritty of Sand

Welcome to Martha's Vineyard, where the ocean comes right up to the shore, and the sand is so friendly it hops into your car and comes home with you.

You're going to encounter a lot of sand on your visit to the Vineyard, whether you're just biking through to see the sights in an afternoon, or are considering something more serious, such as making an offer on West Tisbury. But even though it is everywhere on the Island, as a topic for conversation sand is sadly neglected. And that's really too bad. Sand is a fascinating subject.

Ah, but what is sand? Chopped ham? No, it's chopped rock! Geologists define sand as mineral, rock or soil particles that range in diameter from two millimeters down to one-sixteenth millimeter.

Chop your rock any finer and you've got silt, say the scientists. Chop it coarser and you get your granules, your pebbles, your cobbles and your boulders. But for our purposes, there's a simpler definition: Sand is any particle that hops into your kid's sneakers the minute he steps outdoors on the Vineyard, and then onto the nearest rug as soon as he steps inside.

You can make your own sand quite easily from rocks with a household ballpeen hammer, but here on the Vineyard that hardly seems necessary. Ocean waves and currents are constantly eroding rock into sand. The grinding action of glaciers is another important source of sand, though we haven't had a good glacier in the neighborhood for ages. Then there's the erosive effect of weather, and weather occurs on the Vineyard quite regularly.

Most sand is chopped quartz, if you want to get specific: Quartz is one of the most plentiful substances on earth. It is very hard and durable, and not soluble in water -- which comes in handy along the ocean. Also, to quote the geologists, "sand has practically no cleavage, so it is not readily worn down." This, incidentally, is why you almost never see sand wearing bikinis.

Despite the fact that we leave it lying all over the place, sand is a valuable commercial product. It is used to make cement, window panes and the silicon chips that make your pocket calculator go. According to the government, 416 million short tons of sand having an average value of $1.12 per ton were sold or used by producers in the United States in 1968. Of course, that was before the devaluation of the sand dollar.

Another popular misconception is the image of sand as a sedentary, stay-at-home substance like its lethargic larger brothers, your granules, cobbles, pebbles and boulders. In reality, individual grains of sand -- tagged by geologists using techniques too arcane and plain silly to go into here -- have been clocked moving along shore, carried by the action of waves, at speeds of almost three kilometers per hour.

So when you leave the Vineyard you'll surely be taking a little bit of the Island with you. It's been calculated that the amount of sand a child deposits when he climbs into the family car is roughly half a pint multiplied by the square root of his shoe size.

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