# Mineral Development Act (Northern Ireland) 1969, Paragraph 1


Conglomerate; grit (or gritstone), sandstone, greywacke, siltstone, mudstone, shale (excluding alum shale and oil shale), slate, limestone (including chalk), dolomite; schist (all varieties except graphite schist), gneiss; granite and porphyry (all varieties except decomposed granite in the form of clay); rhyolite (except decomposed rhyolite in the form of clay); aplite, syenite (and related rocks), basalt (and related rocks), picrite (and related rocks).

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Source: https://www.legislation.gov.uk/apni/1969/35/schedule/1/paragraph/1 (the official version)
Page: https://openlegislation.uk/mineral-development-act-northern-ireland-1969/schedule-1/paragraph-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.