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Geology/snowball garnet


dear sir,
what is snowball garnet.what is it origin? i heard this 1st time so kindly describe .

A snowball garnet (Flett, 1912) is one that contains internal surfaces (visible in thin section as discontinuous lines of inclusions of quartz, magnetite, graphite, etc.) of a characteristic form considered to imply rotation relative to the enclosing matrix during metamorphic growth (Spry, 1963, 1969). The typical internal surface has an S−
The texture is syntectonic and must be distinguished from a somewhat similar appearing helicitic texture which is post-tectonic; curved helicitic textures are not uncommon in albite, chloritoid, staurolite, and andalusite.

The earliest explanation was that the crystal grew in a medium in which deformation was by simple shear (Spry, 1963) and growth took place by a process analogous to a snowball rolling down a snow-covered slope. However, this hypothesis appears incompatible with some evidence and details of origin a ...
   Cox, F. C., 1969, Inclusions in garnet: discussion and suggested mechanism for growth of syntectonic garnets, Geol. Mag. 106, 57–62.
   Flett, J. S., 1912, Petrography of the older igneous rocks, in B. N. Peach, W. Gunn, C. T. Clough, L. W. Hinxman, C. B. Crampton, and E. M. Anderson, The Geology of Ben Wyvis, Carn Chuinneag, Inchbae and the surrounding country, Mem. Geol. Surv. Scotland, 89–112.
   MacQueen, J. A. and D. Powell, 1977, Relationships between deformation and garnet growth in Moine (Precambrian) rocks of western Scotland, Bull. Geol. Soc. Am. 88, 235–240.CrossRef
   Powell, D. and J. E. Treagus, 1970, Rotational fabrics in metamorphic minerals, Mineral.

Mag. 37, 801–814.

The Origin and Significance of Snowball Structure in Garnet



Sigmoidal lines of inclusions (snowball structure) indicate syntectonic crystallization and are due to the rotation of the crystal during growth. The sigmoidal trends form spirals whose mathematical properties may be determined. Structural analysis of garnets from Tasmania and Scotland shows that the spirals are a variant of the Archimedes spiral and the forms of the two examined are given by r2=aθ and r3=θ respectively, where r is the radius of the crystal, a is a constant, and θ is the angle of rotation in radians. The amount of movement (slip) along the foliation to cause the measured rotation of the crystal may be calculated but is approximately 30 per cent greater than the length of the visible spiral.

   © Oxford University Press

   Ramsay, J. G., 1962, Geometry and mechanics of formation of “similar” type folds, J. Geol. 70, 309–327.
   Spry, A., 1963, Origin and significance of snowball structure in garnet, J. Petrol. 4, 211–224.
   Spry, A., 1969, Metamorphic Textures. Oxford: Pergamon.
   Wilson, M. R., 1972, Strain determination using rotational porphyroblasts, Sulitjelma, Norway, J. Geol. 80, 421–431.CrossRef

   Gneiss; Metamorphic mineral grow


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Dr D.Venkat Reddy


Engineering Geology,Mining geology,commercial petrology,Decorative and dimensional stones,Hydrogeology


20years texhing and reserch expireience in geology,enginnering geology for graduate and undergraduate students-reserch guidance,10years field exoireience conducting field camps for geology students=Presently Assistant professor in geolog

NITK-National Institute of Technology,Surathkal,Mangalore-DK,India Geology section Dept of Civil Engineering

published 70 research papers.( 4 books)- Editor in Chief-International Journal of Earth Sciences and Engineering -1.Engineering Geology for civil Engineers-oxford &IBH pub-1996] 2.Decorative and dimensional stones of India-CBS Pub-1997 3.Engineering Geology-Vikaspublishers2010 4.Applied Geology-Vikaspub-2010

MSC(GEOLOGY),Osmania university,India, MSC(Tech )Hydrogeology,OU,India PhD(GEOLOGY)OU,India

Awards and Honors
Distinguishing Indian Award Editor in chief-International Journal of Earth Sciences and Engineering (

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PRESENTLY WORKING =Professor of Geology-Dept of Civil Engineering NITK-INDIA

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