56 
NATURAL HISTORY. (Minerals.) 
[north 
Sec.; —the anorthite from Vesuvius;—the oligoclase, also called natron- 
spodumen, to which may be referred the crystals occurring in several 
varieties of porphyry;—the lahradoritefeldspar (also called opalescent 
feldspar, from its often exhibiting a beautiful play of colours in cut 
and polished specimens, of which a pretty complete suite is added), 
chiefly from the coast of Labrador and from the transition syenite 
of Laurwig in Norway * ;—together with some other species separated 
from orthoclase. To these is added the leucite or amphigene, chiefly 
from Vesuvius, in separate crystals of various sizes and degrees of 
transparency, massive, embedded in pyroxenic and other lavas. 
Case 31. Among other mineral substances here deposited, and 
partly belonging to the preceding section, are, the tripliane or spodu- 
men and the petalite: in which latter substance lithia was first dis¬ 
covered by Arfvedson;—the davyne of Monticelii;—the nepheline, 
from Mount Vesuvius, with which are now combined several varieties 
of the eicEolite or fettstein of Werner;—the wernerite, under which 
name, formerly confined to some varieties of common and compact 
scapolite, are now by most mineralogical writers united the meioniie 
of Vesuvius, and the greater part of the scapolite, the parantkine, the 
dipyre, the nuitallite, the hergmannite, the roseUite, and the amphodelite; 
substances which, together with several others provisionally placed in 
this Case, stand in need of further investigation as to their chemical 
and crystallographical characters. 
The cordierite, also known by the names of pelioma, iolite, and dichro- 
zYe, massive and crystallized, from Cabo de Gata, from Greenland, Boden- 
mais in Bavaria, and Orayervi in Finland {steinheilite') ;—the sordawa- 
life from Finland;—the called also grenatite and cross-stone, 
among the specimens of which may be specified the fine mackled 
crystals from Brittany, and the modifications of the simple crystals 
from St. Gothard, accompanied by prisms of disthene, perfectly simi¬ 
lar to those of the staurolite, and sometimes longitudinally grown 
together with them. 
Case 32 contains chiefly 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 distinctive 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 (biotite 
of Hausmann), which has but one axis: in characteristic specimens 
from various localities, particularly from Vesuvius, where it occurs in 
small, but brilliant and transparent six-sided prismatic crystals; and 
lithia-mica, which besides the beautiful peach-blossom, red, violet, 
greenish-grey, and white scaly varieties known by the name of lepidolite, 
(some varieties of which, how^ever, are referable to the silicates com¬ 
bined with fluorides, in Case 58 A,) from Rozna in Moravia, also 
comprises several large-foliated varieties of what was formerly con¬ 
sidered as common mica, such as that from Zinnwald in Bohemia 
and Altenberg, accompanied by apatite, tinstone, and topaz. 
The species and varieties of the talc-like substances are likewise very 
imperfectly understood. Among the specimens of talc in this Table 
* The top of the small octagonal table, standing near Case 30, is a slab of opales¬ 
cent feldspar from Finland. 
