108 
NATURAL HISTORY. 
[long 
and a yellow naker feldspar with reddish dots has obtained 
the name of sun-stone, which is also sometimes given to 
the beautiful avanturino variety of common feldspar placed 
in this glass-case. 
Case 30. Feldspathic substances continued:— ice-s^par 
and sanidine or glassy feldspar, both nearly allied to com¬ 
mon feldspar ; albite, or cleavelandite, the finest specimens 
of which are those from Dauphine and Siberia, and peri - 
cline, united by some mineralogists with the preceding 
species, from St. Gothard, Tyrol, &c.;— anorlhite from 
Vesuvius;— oligoclase , also called natron-spodumen—to¬ 
gether with some other species separated, perhaps unne¬ 
cessarily, from common feldspar and cleavelandite;— leu - 
cite or amphigene, chiefly from Vesuvius, in separate crys¬ 
tals of various sizes and degrees of transparency, massive, 
embedded in pyroxenic and other lavas;— triphane or spo- 
dumen and petalite: substances in which lithia, or the oxide 
of lithium, was first discovered by Arfvedson. 
Case 31. This Case contains— nepheline , from Mount 
Vesuvius, with which are now combined several varieties 
of the elceolite or fettstein of Werner ;— wernerite, under 
which name, formerly confined to some varieties of com¬ 
mon and compact scapolite, are now united the meionite of 
Vesuvius, and the greater part of the scapolite of Werner, 
the paranthine and also the dipyre ; substances which, to¬ 
gether with several others provisionally placed in this 
glass Case, stand in need of further investigation as to their 
chemical and crystallographical characters. 
Case 32 contains micaceous and talcose substances. 
Our imperfect knowledge of the optical properties and 
chemical constitution of many varieties of the former, does 
not admit of their being arranged according to those distinc¬ 
tive characters ; such varieties as have been more closely 
examined in this respect, may be divided into potassa-mica 
(by far the most common), which has two axes ; magnesia- 
mica (from Vesuvius, Siberia, and Monroe, in New York), 
which has but one axis;—and the lithia-mica , which, be¬ 
sides the beautiful peach blossom, red, violet, greenish- 
grey, and white scaly varieties known by the name of lepi- 
dolite, from Rozna in Moravia, likewise comprises several 
large-foliated varieties of what was formerly considered as 
common mica, such as that from Zinnwald in Bohemia and 
