ASSOCIATED MINERALS AND ALTERATION PRODUCES. 67 
chromite and spinel, the former having- Ihhmi found in nearly every 
peridotite that has been examined. These in turn are differenl from 
the minerals in other rocks, such as the limestones. 
'2. The minerals that have been prcxhiced by contact metamoi-phism 
will, in some instances, include the cornndum itself and other min- 
erals, such as biotite, nuiscovite, o-arnet, stanrolite, tourmaline, rutile, 
etc. These minerals Avould result in such cases as that described on 
page 53, Avliere corundum is found in a zone of biotite, which is the 
result of contact metamorphism produced by the intrusion of the 
harzburgite (saxonite) on the gneiss. 
3. The minerals produced by regional metam()rj)hism would be 
those found with corundum in rocks such as the scl lists and gneisses, 
and Avould include biotite. muscovite, amphibole (uralite). silliman- 
ite, cyanite, etc. 
-1. From the minerals mentioned in these three gi'oups others would 
be produced by direct or indirect alteration. The minerals resulting 
from the alteration of the mineral constituents of granites, syenites, 
gneisses, schists, etc., are not a!)uiidant, as neither these mineral^ 
nor the corundum itself has usually suffered any very great alteration. 
The felds})ar is simietimes more or less kaolinized, and this \you1(1 rep- 
resent the chief alteration product. 
5. Minerals that are direct alterations of corundum are not com- 
mon, the i)rincipal ones being diaspore, muscovite, and magnetite. 
With tlie i)erid()tites and other basic magnesia n rocks, however, 
the alteration products are much more numerous, and thus the asso- 
ciated minerals of corundum, which are directly the result of the 
alteration of the mineral constituents of the peridotite, are also 
numerous. These, again, will depend upon the clniracter of the 
peridotite or other basic magnesian rock as to whether it is d unite, 
composed almost entirely of chrysolite (olivine), or enstatolite, com- 
posed almost entirely of enstatite, or one of the other peridotites or 
pyroxenites, which are composed of two or more minerals. 
The primary minerals occurring with the corundum also cause a 
considerable variation in the alteration minerals, as. with felds[)ar, 
kaolin Avill ])e a common alteration product, and, more rarely, such 
minerals as wellsite and chabazite, two zeolites found at Buck 
Creek mine. Clay County, X. C. At nearly all of the corundum 
deposits occurring in the jKM'idotites, pyroxenites, and am})liibolites 
some minerals of the chlorite or clintonite gr()ui)s are common altera- 
tion products, and there is a noticeable absence of any quantity of 
I quartz or of the micas of the nuiscovite grouj). There is, however, a 
considerable variation in the minerals associated with the corundum 
at various localities. Thus corundophilite, which has been so com- 
1 monly observed associated with .corundum and emery at the locali- 
I ties in Asia Minor and at Chester, Mass., has not been identified in 
