2§4 CLAY GENUS. Olfervations. r. 1 he difintegrated condition of this kind of felfpar is owing in many inftances to weathering ; but it is alfo highly probable that it is often originally formed in a fimiiar hate. 2. It is the link which conne&s felfpar with por celain clay. We obferve a diminilhing fufrbility from com- - tnon felfpar through difintegrated felfpar to porcelain clay, which depends, according to Werner, on the relative proportion of alkali in each. if"" Geognottic Situation of common fefpar. It h ore of the mod abundant o f fofiils. It firms a coni.ituent part < f granite and gneils ; itoccurs a'lo in firmi’e, in grecnhone, md in imbedded cryitals in porphyry, bafvlt, and porphyry flafe. It al o '.ccurs in beds and kidneys in primitive mountains, and in veins of the olueit formation. Geographic Situation of common felfpar. It is fo univerfally diftributed that we fhall only mention the localities of a few of the mod remarkable varieties. The beautiful green coloured variety is found
