578 GEOTECTONIO (STRUCTURAL) GEOLOGY. [Boox IV. 
and there porcelainized, while its shells (producti, &c.), though nearly 
obliterated, are still traceable by their impressions. In the altered 
fossiliferous shale numerous crystals of analcime and garnet have been 
developed, the latter yielding as much as 20 per cent. of lime.’ Similar 
phenomena were observed by Sedgwick along the edges of intruded 
basalt among the Carboniferous limestones and shales of High Teesdale. ? 
Among localities where the development of new minerals in proximity 
to eruptive rock has taken place on the most extensive scale, none 
have been more frequently or carefully described than some in the 
group of mountains lying to the east and south-east of Botzen, in the 
Tyrol (Monzoni, Predazzo). Limestones of Lower Triassic (or Permian) 
age have there been invaded by masses of monzonite (a rock intermediate 
between syenite and diorite, sometimes containing much augite), granite, 
melaphyre, diabase, and orthoclase porphyry. They have become coarsely- 
crystalline marble, portions of them being completely enveloped in the 
eruptive rock. But their most remarkable feature is that in them and 
in the eruptive rocks’ in contact with them many beautifully crystal- 
lized minerals have been developed, including garnet, idocrase, gehlenite, 
fassaite, pistacite, spinel, anorthite, mica, magnetic iron, hematite, — 
apatite, and serpentine. Some of these minerals occur chiefly or only 
in the eruptive masses, others more frequently in the limestone, which 
is marked by a lime-silicate hornstone zone along the junction. But 
these are all products of contact of the two kinds of rock. Layers of 
carbonates (calcite, also with brucite), alternate with laminz and streaks 
of various silicates, in a manner strikingly similar to the arrangement 
found in limestones among areas of regional metamorphism, where no 
visible intrusive rock has influenced the phenomena. 
Production of foliation.—This is the most complete kind of 
metamorphic change, for not only are new minerals developed but the 
whole texture and structure of the rock are altered. Reference has 
been already (p. 541 seq.) made to the striking manner in which foliation 
has been superinduced upon ordinary sedimentary rocks round large 
bosses of granite. The details of this change deserve careful 
consideration, for they possess a high importance in relation to any 
theory of metamorphism. 
A classical region for the study of this kind of alteration is in the 
Harz, where, round the granite masses of the Brocken and Ramberg 
the Devonian and older Paleozoic rocks are altered into various flinty 
slates and schists which form a ring round the eruptive rock. Dykes 
and other masses of a crystalline diabase have likewise been erupted 
through the greywackes and shales, which in contact and for a varying 
distance beyond have been converted into hard siliceous bands (horn- 
stone) and into various finely foliated masses (Fleckschiefer, Band- 
schiefer, Contact-schiefer, the spilosite and desmosite of Zincken). The 
' Cambridge Phil. Trans. i. p. 402. 
Sh Grol? selene Doelter, Jahrb. Geol 
n the Monzoni region, see Doelter, Jahrb. . Ret , 
wliéte a bibliography of the locality up to the date of ubllentich wit be found. Bar 
1875 other papers have appeared, of which the following dealing with the plienomena of 
contact-metamorphism may be mettioned, G. youn Rathi, Z. Deitsel. Geol, Ges, 1875 
p: 843, Lieiiiberg, Op, cit, 1877, p. 457. : es. 1879; 
