- Supergene: post-mining oxidation & weathering deposits
- Crumlin Colliery, Ebbw Vale, Gwent: white, powdery efflorescence (Bevins, 1994) on, Natural History Museum specimens B.M. 1985,MI 33592 and B.M. 1985,MI 33593 from Seam ‘x’, Ebbw Vale Main, and ‘40 yd outbye 1st ¾ crosscut on Ebbw Vale Return’ are described by Bevins (1988).
- Parys Mountain, Anglesey: beige coloured powdery szomolnokite occurs in association with silky white fibrous halotrichite on National Museum of Wales specimen, no. NMW 75.38G.M.5, labelled as 'Main Lode, Parys Mountain' (Cotterell, 2009).
- Trwyn Cae Iago, near Porthmadog: Cotterell (2009) identified a beige coloured powdery phase in association with white fibrous halotrichite and yellow jarosite on National Museum of Wales specimen no. NMW 79.10G.M.2 as szomolnokite.
There are no key localities for this specimen.
- Bevins, R.E., 1994. A Mineralogy of Wales National Museum of Wales, Geological Series No. 16, Cardiff, 146pp.
- Bevins, R.E., 1988. Sixth supplementary list of British Isles minerals (Welsh). Mineralogical Magazine, 52, 121-124.
- Cotterell, T.F., 2009. A review of halotrichite group minerals in Wales. UK Journal of Mines and Minerals, 30, 43-47.
There are no references for this specimen.