70 natural history. (Minerals.) [north 
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, which has but one 
axis : in characteristic specimens . from various localities, particu- 
larly from Vesuvius, where it occurs in small, but brilliant and transpa- 
rent six-sided prismatic crystals ; and lithia-mica, which besides the 
beautiful peach-blossom, red, violet, greenish-grev, and white scaly 
varieties known by the name of lepidolite , (some varieties of which, how- 
ever, are referable to the silicates combined with fluorides, in Case 58 A,) 
from Rozna in Moravia, also comprises several large-foliated varieties 
of what was formerly considered 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 like- 
wise very imperfectly understood. Among the specimens of talc in this 
Table Case may be specified the common or Venetian (which enters 
into the composition of cosmetics), and the indurated talc; to the former 
of which may probably be referred the green radiated talc from Siberia, 
composed of distinct groups of small diverging laminae, and which is 
known under the name of pyrophyllite ; — potstone, ollite, or lavezzo, (the 
lapis comensis of Pliny,) which appears to be an intimate mixture of 
talc and asbest, chiefly from Chiavenna, near Como, where it is 
manufactured into culinary vessels; — chlorite, crystallized in ag- 
gregated, small, modified rhombic prisms ; the earthy and foliated 
varieties, coating crystals of octahedral magnetic iron-stone, &c. ; 
chlorite slate ; — the scarce leucktenbergite from the Ural, the composi- 
tion of which appears to approach near to that of chlorite ; — pinite, 
crystallized in regular hexagonal prisms, and gieseckite , from Green- 
land, which appears to be a variety of this species. — Fahlunite or 
triclasite, from Fahlun in Sweden, This latter mineral substance, how- 
ever, together with the weissite, the chlorophyllite, the praseolite , and 
the aspasiolite, as also several varieties of the pinite in this Table Case, 
are now by some mineralogical writers considered as only metamor- 
phoses of cordierite (Case 86). 
Case 83. This and part of the following Case chiefly contain 
amphibolic and pyroxenic and related minerals, among which may 
be specified the basaltic and common hornblende, including the parga - 
site ; the actinolite or strahlstein (divided by Werner into the glassy, 
common, and fibrous varieties, and to which also belongs the ka- 
rinthine of this author) ; — the grammatite or tremolite (so called from 
Val Tremola, where, however, it is not found), among the specimens 
of which are the fine, fibrous varieties, resembling asbest ; the glassy 
tremolite, in dolomite and granular limestone, &c. — Arfvedsonite — ra - 
philite, &c. . 
Case 84. Part of this Case is occupied by the mineral substances 
called asbestine , many of which pass into some of the varieties of horn- 
blende ; others, both asbest and amianth, are modifications of the state 
of aggregation of different amphibolic substances , and to these Breit- 
haupt° also refers his kymatine, metaxite, peponite, and pycnotrope. 
Among them may be observed specimens illustrative of the transition 
from a very close to a loose fibrous structure ; — several varieties of the 
■flexible asbest or amianth , with some antique incombustible cloth, 
paper, &c., made of it;— the varieties called common and schiller- 
