Conversations on Mineralogy. 150 
P. 183. Zoisite very much resembles epidote in some respects, and 
the constituent parts are nearly the same, but its colour is generally bluish 
or yellowish gray, sometimes inclining to brown. 
Frances. 1 think the fracture is brighter than the epidote. 
Mrs. L. The most distinctive character of zoisite, is the manner in 
which the prismatic crystals are aggregated, like a parcel of reeds beside 
each other, and sometimes slightly diverging. It has but one cleavage, 
which is parallel to the axis of the prism, and in the direction of the 
shorter diagonal of the base. 
P.235. Hornblende, actinolite, and tremolite, are in some respects so 
much alike, that many mineralogists consider them as varieties of the same 
substance, their difference being chiefly occasioned by the nature of the 
minerals in which they are imbedded; but as this cause produces great 
difference of colour, and even of composition, it will perhaps be better 
to divide them. 
Frances. But would not the form of the crystals decide this question ? 
Mrs. L, Their crystallization has, ultimately, shown their connexion : but 
the first crystals of tremolite that were examined, not being very perfect, 
their angles were found by the common goniometer, (which was the only 
one then known,) to differ from those of hornblende and actinolite by, L 
think, two degrees. I speak of the angles of the prism, which was sup- 
posed to be the primitive form, for the terminations of the crystals were 
altogether different from those of hornblende: The examination of other 
crystals has since proved that the primitive form of all the three species is 
an oblique prism, of which the incidencies of thelateral planes are 124° 36/, 
and 55° 24’, by the reflecting goniometer. 
Mary. From what you have said, I suppose these minerals passinto each 
other. 
Mrs. L. Yes, they do, in every respect. Actinolite is intermediate be- 
tween hornblende, which is generally black,or very dark green, and tremo- 
lite, which is always a light-coloured mineral. Actinolite is always green. 
P. 247.—Mary. I recollect you told us that tale might be distinguished 
from mica by being flexible, but not elastic; but when the laminz are so 
small as in this specimen, you would not be able to see whether they were 
elastic. 
Mrs. .. Perhaps not, but tale and mica differ in other particulars, as 
well as their degree of flexibility. If you try to scratch mica, you will 
feela harsh grating sensation ; but tale is very soft and soapy, yielding to 
the pressure of the nail with ease. This is the case even with indurated, as 
well as fuliated and earthy talc; besides, the lustre is more pearly than 
that of mica, and in general the colour is white or green. 
Frances. This is a beautiful bright green, but I do not see any large folia, 
like your Siberian mica. 
Mrs. L. No; the lamine of tale rarely exceeds a few inches in size. 
When it is crystallized, which is more rarely the case than with mica, it 
has the same form as mica. ‘The substance commonly called French chalk 
is indurated talc. 
A few puerilities now and then occur, which perhaps the 
plan of the work has almost unavoidably introduced, and may 
be some objection to the plan itself, for, if necessary to the 
keeping of the piece, they imply an infantine state of intellect, 
ill adapted to the comprehension of the more difficult parts of 
the subject. The style, as our extracts have shewn, is easy, 
clear, and unaffected. There are two appendices at the end 
of the work, one containing the tabular arrangement of the 
subject, the other an exceedingly useful, “ Alphabetical list of 
one hundred and eighty-seven names of minerals, with their 
