52 ANKERITE VEINS OF LONDONDERRY—1LOUIS. 
Breithaupt gives 2 Fe Cos + Mg Cos as the formula for his 
Sideroplesite, and the following as its composition :— 
Carbonic Anhydride.....-.... 41,93 
Nerrods Omid ey renee eat 2 4.5.06 
Maomesiatvciss x Ses sami: ie a 12.16 
9915 
Thus, the composition as well as the physieal characters of 
our Nova Scotian minerals approach very nearly to those of 
Breithaupt’s Sideroplesite, more nearly in fact than to those of 
any other mineral that I know of, and I think that there can be 
little doubt but that it should be referred to this variety. Hav- 
ing regard, however, to the very large quantities of this mineral 
lately discovered at Londonderry, to its well defined chemical 
composition and physical characters, 1 would venture to suggest 
that Sideroplesite is fully entitled to be classed as a well defined 
mineral species, rather than as a mere variety of Siderite. 
The following is an analysis of a sample of mixed Ankerite 
and Sideroplesite, taken from a large deposit of mineral, in 
which both species were present, in one of the upper levels of 
the West Mines :— 
Misoluble Matter 2s oie ys 0.3 
Calcie Warbomatet.— . ise. ee 27 52 
Ferrous Hel bat banat en Sn Cl 46.09 
Wanvanous (er ,,/) tow tccetieee tear 2.28 
Magtiesic “ wig lahat rears ROSCOE 
100.00 
This composition corresponds to the formula 2 Ca Cos + 3 Fe 
Co; + Mg Co3; equal to a mixture of about five parts of An- 
kerite and six of Sideroplesite. 
These two are by far the most abundant of the minerals 
occurring in these veins, the rest being present only in small 
quantities, and usually near the walls. 
3rd.—Barytes.—This mineral occurs in fissures in the ae erite 
veins, occasionally in small tabular crystals, but more often in 
Sete 
