120 The Americdii Geolo<jifif. August, LS9 5. 
making? constituent of a rather massive outcrop of crystalline schist. 
The associated minerals are mirgarite, in which the new mineral is fre- 
quently imbedded, epidote, actinolite, glaucophane and red garnet. 
Lawsonite is orthorhombic in crystallization, and its axial ratio is a:b:c 
=.6652 : 1 : .7,385. It jjossesses two fairly distinct habits, the crystals oc- 
curring in cavities show a strong development of the prismatic faces, 
while those imbedded in the margarite are usually larger and have a 
prevailingly tabular habit, the basal plane being well developed. A per- 
fect cleavage exists parallel with the brachypinacoid and a sub-perfect 
cleavage parallel with the base, while an imperfect jjrismatic cleavage 
can sometimes be seen in thin sections. In optical character the min- 
eral is positive and the axial plane is the brachypinacoid. In certain 
basal sections pleocroism is strong, but in sections of the ordinary thick- 
ness it is rarely detected. In thin sections of the schist the bright po- 
larization colors and high relief of the mineral are decidedly striking. 
The specific gravity is about 3.085, and the hardness is 8. The chemical 
formula deduced from two analyses is H^ CaAl., Si., Oj,^,, being similar 
to carpholite (H^ MnAU Si^ Oj|j). The possibility of the isomorphism 
of the two minerals is suggested. Lawsonite is named in honor of Prof. 
Andrew C. Lawson of the University of California. u. s. g. 
Post-Laramie Deposifs of Colorado. In the volume recently issued 
by the Colorado Scientific Society* there are several papersf which add to 
our knowledge of this interesting series of beds. It will be remembered 
that in 1888 Eldridge and CrossJ described the Arapahoe and Denver 
formations as post-Laramie. At the same time Cannou§ announced the 
discovery of Tertiary Dinosauria in the Denver beds and Hills || shortly 
after described Tertiary beds from the Huerfano River basin consider- 
ing them as Eocene but recognizing their probable contemporaneity, in 
part at least, with the Denver and associated beds. In 1889f he gave 
additional notes on the Huerfano beds. In 1893 Cannon** noticed the 
description by Marshtt of the dinosaurian remains found at Denver and 
similar remains from Montana, and in the same year HillsJJ discussed 
the beds already described and added considerable information regard- 
ing contemporaneous deposits. The original paper by Cross was re- 
vised and republished in the American Journal of Science§§ and more 
recently he has described i| || the whole subject of the post-Laramie. 
The post-Laramie beds are not confined to Colorado but similar de- 
posits have been noted by Canadian geologists and Weedl: ^ has recent- 
*Proc. Col. Sci. Soc, iv, 1891, 1892, 1893. 
tRemarks on the Classification of the Huerfano Eocene ; by R. C. Hills ; pp. 7-9. 
The Post-Laramie Beds of Middle Park, Colorado; by Whitman Cross; pp. 192-214. 
Geolof?y of Denver and Vicinity ; by Geo. L. Cannon, jr. ; ijp. 224-2::i4. 
tProc. Col. Sci. Soc, in, i, 86-118, 119-1:«. 
§Ibid., 140-147. 
Illbid., 148-164. 
Tllbid., Ill, i, 217-223. 
**Ibid., Ill, iii, 2.V.5-254. 
t+Am. Jour. Sci., r.i), xxxix, 81-86, .Jan., 1>.9(). 
tIProc. Col. Sci. Soc, iii, iii, :J88-:i97. 
§§Am. .Jour. Sci., (S), xxix, 281-282, 1889. 
|i ilbid., XLiv, 19-42, 1892. 
l^tBull. U. S. Geol. Surv., No. 105. 
