Gemstones in the Bilge

We don’t usually get excited about things we find in the bilge. But during a haulout last summer we were astonished to discover a trove of ‘sparkling gemstones’ beneath the floorboards of our trimaran. Okay, so they turned out to be only salt crystals, but we were fascinated by their presence there nonetheless. 

Evidently there’d been an ever-so-slight seepage of sea water around two throughhull fastenings attached to a no-longer-used SSB ground plate. Over time, the water had evaporated away, leaving only the salt (sodium chloride), which eventually formed into perfectly square crystals, some of which were more than an inch across. Finding them was definitely the highlight of that day’s boatwork, even though we were a bit horrified to learn that our boat had been taking on water, albeit a miniscule amount, without our knowing about it.

If there are any scientists reading this, we’d love to know why salt crystals form into perfect squares, as compared to the more irregular form of other crystals, and why some grow so large, while others remain tiny. Please email us here with your insights.