10 Geology and Mineralogy of apart of Massachusetis, &c. 
Yo designate the rock intended by an observer, it is neces- 
sary to resort to the several subdivisions. 
he hornblende rocks of this section are all primitive. 
They are 1. Hornblende and Hornblende slate, occurring 
as rocks, in which the hornblende is “ nearly or quite 
ure.”* 2. Primitive Greenstone, or aggregate of horn- 
blende and feldspar, in which the “ hornblende predomin- 
ates, and very frequently gives to this aggregate more or 
less of a greenish tinge, especially when moistened.”* This 
mineral often has a slaty structure, forming a variety, prim- 
itive Sratesions slate. ‘These rocks are always cee 
ith “f gneiss, mica-slate, or argillite.”* 3. Hornblende 
and Mica, the former in larger quantity and someting’ a 
little feldspar. It may be called micaceous primitive trap, 
or micaceous greenstone, with more propriety. 
The preceding rocks are abundant along the eastern part 
of the ergo often associated, and always in beds in the mi- 
ca-slat hey are too abundant to need a specification of 
their localities: though I have not observed them to form 
very large beds. About a mile east of the meeting house 
in Middlefield is a beautiful greenstone slate. Indeed that 
town, as well as the others in that line, contains all the above 
varieties of primitive trap.t 
Associated with these rocks, is 
Stenite. 
This is an aggregate of hornblende and feldspar, in which 
the ‘feldspar is the most abundant ingredient, and the 
quantity of horablendas is sometimes small.”* I have never 
observed this sete in | great quantities. It is sometimes 
porphyritic. In s’ Cyc. it is stated that the feldspar of 
the real sienite is of a ee color. In what is called Sie- 
* Cleaveland’s Min. and Geolp 743, 745, and 750. The composition 
: ee rocks, given in Rees’ Cre is the ce as that quoted from this 
+ On the nigh marshes, in the es pl sen blag rest on this rack and 
mica-slate, is found the rare plant, Eriophorum cespitosum, and in 
Stockb ridge i “eg an eleyated marsh < the foot of a hill of sniodaiete grows 
the E riophorum a alpinum, L. and Carex lenticularis, Mx. 
