Mineral Environments
- Tawites -

     "The tawites (incorrectly called sodalite xenoliths, inclusions) have produced the largest addition to the growing list of MSH minerals in recent years. These xenoliths were first encountered in a zone of nepheline syenite in the Poudrette quarry in 1982. Since then, the quarrying operations have intermittently exposed parts of the same zone on different levels of the quarry. The nepheline syenite in which the xenoliths occur is generally fine-grained, dense, dark gray to brownish gray in color, significantly different in appearance and texture from most of the nepheline syenite found in MSH, which may be due to its close proximity to fine-grained and dark gray to dark green zones of hornfels".*

    "The tawites consist mostly of masses of white to colorless to pale violet (photochromic) coarse grained sodalite with small concentrations of villiaumite, eudyalite, ussingite, pyroxenes and a large array of very rare and unusual minerals. The xenoliths are angular to spherical or oblong in shape, ranging in size from 5 cm to about 1m across, randomly distributed in the nepheline syenite, and in some areas constituting close to 50% of the volume of the rock".*

Tawite - click for larger pic
Tawite from MSH
© Quintin Wight

     "The minerals occur embedded in massive sodalite or in small randomly distributed, irregularly-shaped cavities rarely exceeding 1 cm in their largest dimension. The mineralogy of these xenoliths is unique and many of the minerals found in this association have not been encountered in the other modes of occurrences at Mont Saint-Hilaire".*



Minerals found in tawites
Aegirine
Alabandite
Albite
Analcime
Anatase
Ancylite-(Ce)
Arsenopyrite
Astrophyllite
Barytolamprophyllite
Bismuth
Britholite-(Ce)
Burbankite
Calcite
Cancrinite
Catapleiite
Chabazite
Chkalovite
Cryolite
Dorfmanite
Epistolite
Erdite
Eudialyte
Fluorapatite
Fluorite
Galena
Garronite
Gmelinite
Gonnardite
Graphite
Griceite
Halite
Harmotome
Kogarkoite
Kupletskite
Lamprophyllite
Löllingite
Lorenzenite
Lovozerite
Lueshite
Makatite
Mangan-neptunite
Microcline
Molybdenite
Nahpoite
Natrite
Natrolite
Natron
Natrophosphate
Nepheline
Parakeldyshite
Paranatrolite
Paraumbite
Pectolite
Petarasite
Phillipsite
Pyrochlore
Pyrophanite

Raite
Rasvumite
Revdite
Rinkite
Sazhinite-(Ce)
Searlesite
Sérandite
Shortite
Sidorenkite
Sodalite
Spertiniite
Sphalerite
Steenstrupine-(Ce)
Terskite
Tetrahedrite
Thalcusite
Thermonatrite
Thorogummite
Titanite
Trona
Tugtupite
Ussingite
Villiaumite
Vinogradovite
Vitusite-(Ce)
Vuonnemite
Wurtzite
Yofortierite

* From Mineralogical Record Vol 21, Horváth L. and Gault R.A.