I was in Northern Ireland last weekend for Heritage Open Days and one of the locations I visited was Toome Bridge for a guided history tour along the towpath of the Toome Canal.
One of the historical aspects of the town covered by the guide was the processing of kieselguhr in the town (known as diatomite in English). Diatomite is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. When nitroglycerin is absorbed in diatomite, it becomes more stable and can be transported. This was discovered by Alfred Nobel and patented as dynamite.
As I update the gazetteer for the railway stations visited last weekend (Derry Central Railway and the Belfast & Ballymena branch from Drumsough to Magherafelt), I noticed the presence on the historical 6 inch maps online at Toome of “Kieselguhr Works” north of the town.