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In the Lake Superior copper district, porcelaneous datolite occurs both as crystals and as a porcelaneous material in the native copper deposits contained in the Portage Lake Volcanics. It can be found in fissure veins and brecciated amygdaloidal basalt lodes but not in the conglomerate lodes. Porcelaneous datolite occurs as a fracture-filling forming narrow veins, as masses cementing brecciated basalt and as nodules sometimes resembling the outer surface of cauliflower. The most popular color in a datolite nodule is yellow, which can range from bright canary-yellow through egg-yoke-yellow to dark mustard-yellow. The yellow nodules were produced by only a handful of localities in the Lake Superior copper district, including the northwest side of Isle Royale National Park, Keweenaw Point area, Delaware mine, Pewabic lode, Mass mine and Nassau mine. INSET: Part I: Northern Keweenaw County and Isle Royale National Park.