Mineral Database (Saesneg yn unig)

Mineral Database (Saesneg yn unig)
Mineralogy of Wales

Lizardite

Crystal System: Hexagonal,Trigonal
Formula: Mg3Si2O5(OH)4
Status of Occurrence: Confirmed Occurrence
Distribution: Locally Abundant
Chemical Composition: Magnesium silicate hydroxide
Method(s) of Verification: Anglesey – XRD (Maltman, 1977); Rhiw – XRD (Natural History Museum, no. 5920F).
Chemical Group:
  • Silicates
Geological Context:
  • Hydrothermal : serpentinization
Introduction: lizardite belongs to the kaolinite-serpentinite group of minerals and is one of three minerals (antigorite, lizardite and chrysotile) commonly referred to as ‘serpentine’. Antigorite and lizardite are soft green platy minerals, whereas chrysotile is fibrous. These minerals commonly result from the hydrothermal or retrograde metamorphism of mafic minerals such as olivine, pyroxene or amphibole, in ultrabasic rocks. Lizardite is the most common of the three serpentine minerals and is typically found with brucite and magnetite.
Occurrence in Wales: lizardite has been recorded from two occurrences of ultrabasic rocks in Wales.
Key Localities:
  • Holy Island, Anglesey: lizardite occurs associated with antigorite in serpentinized peridotite bodies within the New Harbour Group (Monian Supergroup) metasediments. Textures show that the lizardite replaces primary olivine and orthopyroxene (Maltman, 1977).
  • Rhiw, Llŷn, Gwynedd: the presence of lizardite, in ultrabasic rocks of the Rhiw Intrusion, has been confirmed by X-ray diffraction analysis.
References:
  • Greenly, E., 1919 The Geology of Anglesey.  Memoirs of the Geological Survey of Great Britain, 980pp (2 volumes).
  • Maltman, A.J., 1977 Serpentinites and related rocks of Anglesey.  Geological Journal, 12, 113-128.