Veins come from the major fault lines where krutovite crystallized at moderate hydrothermal temperatures.
en.wikipedia.org They are predominantly stratiform accumulations of sulfide minerals that precipitate from hydrothermal fluids on or below the seafloor in a wide range of ancient and modern geological settings.
en.wikipedia.org Nontronite forms from the weathering of biotite and basalts, precipitation of iron and silicon rich hydrothermal fluids and in deep sea hydrothermal vents.
en.wikipedia.org It occurs in hydrothermal copper-nickel-iron sulfide bearing veins associated with chalcopyrite, pyrrhotite, galena, sphalerite, pyrite, millerite, gersdorffite and ullmannite.
en.wikipedia.org It occurs in oxidized hydrothermal tungsten-lead ore deposits typically in association with raspite, cerussite, anglesite, pyromorphite and mimetite.
en.wikipedia.org