1192 The American Naturalist. [December, 
species. It is black on a fresh fracture, and has a brownish-yellow 
translucency on thin edges. It has a density of 4.925—5.038, a hard- 
ness of 5.5, and a light yellowish-brown streak. On exposed surfaces 
it alters toa lemon-yellow gummite, with a density 3.354, and hardness 
3.5. An analysis of the crystals from South Carolina gave: 
Cb,O, Aer AE VOe PDO PO FO, UG. Cal) HO 
KENT 0 X47 .18 19.47  .68 4.46 
Ins. SiO 
It 30: und. 
The authors call attention to the fact that the mineral is the first repre- 
sentative of the columbo-titanates in America. The rare mineral 
eukairite has been found in Villa Argentinia, Prov. Rioja, Argentine, 
and at several localities in the Andes, associated with calcite, bornite, 
and other sulphides of copper. It crystallizes in cubic forms (not 
necessarily regularly), and has a density of 7.641-7.661, and a com- 
position, according to Otto,” as follows: Ag= 42.7; Cu=25.5; 
Se =31.5. In general appearance it is like galena. Lacroix?! de- 
scribes the optical properties of quite a numer of crocidolites, and con- 
cludes that the mineral is a variety of hornblende very widely spread 
through rocks of various kinds. It may be distinguished from glauco- 
phane by its positive double refraction on basal sections, and its nega- 
tive refraction in elongated sections. After analyzing a large suite of 
wads and pstlomelanes, Gorgeu? is inclined to regard them as manga- 
nites of various bases, corresponding approximately to the formulas 
3(MnO,)RO + 1-3H,O. Among the wads examined were a few quite 
well crystallized. Four crystals of orthoclase from the porphyritic 
granite of the Fichtelgebirg are described by Müller 3 as interpenetra- 
tion twins, in which each individual is elongated in the direction of its 
-a axis. Their oP faces are in the same plane, so that their combination 
is x - shaped, with the twinning plane a hemi-pyramid. Laspeyres” 
suggests that the ground-form of diotite be made to correspond with 
that of clinochlore, so that the isomorphism of the two minerals may 
be made more apparent. Messrs, Clarke and Schneider? have 
shown experimentally that the zač from Hunter’s Mill, Fairfax Co., 
20 Ber. d. deutsch. chem. Ges., XXIII., 1890, p. 1039. 
31 Bull. Soc. Fran, d. Min., 1890, p. 15. 
2 Ib., p. 21. 
% Zeits. f. Kryst., XVIL., 1890, p. 484. 
^4 Zeits. f. Kryst., XVIL., p. 541. 
235 Ber. d. deutsch. chem. Gesel., XXIII., P- 1537. 
