LIME. 
235 
MARL. 
This substance, which, when pure, contains little else than carbonate of lime, has already 
•been noticed in detail (see page 83). 
ARRAGONITE. 
[From its having been first found in the province of Arragon in Spain.] 
Arragonite. Hauy, Ckaveland, Phillips , Thomson and Shepard. — Prismatic Limestone. Jameson. ■— Prisma- 
tisches Kalk-Haloid. Mohs. — (It has also been called Igloite, Flos Ferri, and Needle Spar. Beudant places 
it as a subspecies under Carbonate of Lime.) 
Description. Colour usually white, but sometimes with a shade of grey, yellow, green 
and blue. It occurs regularly crystallized ; also in prismatic concre¬ 
tions, and massive. The primary form is a right rhombic prism. 
Fig. 101. M on M' 116° 5' {Phillips). Three of the crystals are 
often grouped together so as to constitute a six-sided prism. Cleavage 
parallel with the lateral planes of the primary. Fracture conchoidal, 
passing into uneven. Lustre vitreous, inclining to resinous. Trans¬ 
parent and translucent. Brittle, and even frangible. Hardness from 
3.5 to 4.0. Specific gravity from 2.92 to 2.94. Thin fragments of 
transparent crystals decrepitate in the flame of a candle ; other varie¬ 
ties lose their translucency, and become friable. With borax, it dissolves, and forms a trans¬ 
parent glass, which crystallizes on cooling ; but in soda, it is insoluble. It phosphoresces on 
hot iron, and dissolves with effervescence in nitric and muriatic acids. 
Arragonite oftentimes so closely resembles calcareous spar, that it is very difficult to distin¬ 
guish it. The crystalline form, when it can be determined, is always a safe guide. The 
specific gravity of arragonite is also higher than that of calcareous spar. The blowpipe 
characters cannot, I think, in all cases be depended on. 
From the fact that some of the foreign specimens of arragonite are fibrous, many of our 
fibrous carbonates of lime have received that name in American cabinets. But I have reason 
to believe that arragonite is rare in the United States; there are certainly but few localities of 
it in the State of New-York. 
Composition. The chemical composition of this mineral does not differ from that of cal¬ 
careous spar, except that it contains, in most instances, minute, but very variable, proportions 
of water and of the carbonate of strontia. In ten analyses of Stromeyer, the water varies 
from 0.154 to 0.599, and the carbonate of strontia from 0.509 to 4.013. It is now, how¬ 
ever, ascertained that these last ingredients are not always present, and that the peculiar 
crystalline form of this mineral is not due to them. Indeed, M. Gustave Rose has shown 
that arragonite may be prepared artificially, without the addition of a particle of strontia. 
When a simple solution of carbonate of lime in carbonated water is evaporated in a water 
Fig. 101. 
