heavy sand

Semi-solid sand lumps... all I can say about them is that when we take the kids to the beach they'll spend a good long time fascinated with how the sand "rocks" deteriorate in their hands, there one minute, gone the next. A good lesson in life, no wonder it fascinates so much. My father, a geologist, had plenty more to say about the sand once I mentioned to him that I'd noticed patches of dark sand on the beach at Fort Tilden, and brought some home. He had so much to say and teach about it that I wound up forgetting the purpose of my call, which was to thank him for sending me one of his ceramic dishes.

In his rhapsody about what he called "heavy sand" I learned many things. For instance, a granular deposit formed as an outcome of its weight is called a placer (short a), and the major components of this placer that I'd come across, this patch of sand granules heavier than the granules of quartz that wound up in other places, are very likely magnetite, garnet, hematite and ilmenite. Some heavy sand placers on beaches in South Carolina are mined on account of the high ilmenite content, a source of titanium.

Also, I had an interesting lesson on the differences between magnetite and hematite, both ferous minerals: magnetite formed before there was oxygen on the earth, and hematite, which looks the same as magnetite except it becomes red when scratched, developed after. The potential for red in the hematite is the product of the oxygen incorporated into its molecules thanks to the earliest oxygen producing organisms, blue-green algae, which commonly grew in columns, or rather, accretionary structures called stromatolites in shallow waters in the Precambrian era. Stromatolites are are the oldest known fossils, dating back 3 billion years.

But back to the beach- theoretically, some of this dark sand - the magnetite component - will be drawn to a magnet. I hope to soon discover how magnetic this Fort Tilden heavy is. And also, thanks Dad, if you read this, for the lesson, and the beautiful, sturdy, heavy dish.