Note 122 — EXCURSION V.
Reading edition
The only chemical difference between Cleavelandite and Felspar is, that about 12 per cent. of Potass in the latter is replaced by an equal quantity of Soda in the former. The earthy ingredients in both minerals are the same, and exist in similar proportions. The primary form of each is a doubly oblique prism, but the two prisms differ so essentially from each other in the measurement of their angles, that the substances are easily distinguished from each other by the Goniometer.