114 
For convenience, and to save the reader the trouble of 
turning to the pages of a text-book, a short description of 
Vivianite, otherwise known as Blue Iron Earth, or Native 
Prussian Blue, may be of service. 
II. Descriprion.—Vivianite: (3 FeO, PhO® + 8 HO) formula, 
(Blue Iron Earth.) When crystallized it belongs to the Mono- 
clinic system, and has a hardness of 1°5 to 2, with a specific 
gravity of 2°6 to 2:7. In colour it is usually bluish, or bluish 
green. The crystals are generally green when seen at right 
angles to the vertical axis, and blue when parallel to it; the 
streak is bluish, with a lustre pearly to vitreous, transparent to 
translucent, and opaque on exposure. Besides the crystallized 
state of modified oblique prisms, which mostly occur in metal- 
liferous veins, it is found in radiated, fibrous, reniform, 
globular and earthy states (Blue Iron Earth,) and often found 
coating bodies and as incrustations. This earthy variety is not 
uncommon in peat mosses, especially where animal substances 
have decayed; and, according to Prof. A. Gurxin, it is some- 
times to be observed as a coating on fossil fishes, not unlike 
the bloom ona plum. The chemical composition of Vivianite 
is computed as— 
Hydrous Phosphate of Iron 
— Protoxide of Iron ot ... 42:4 
Phosphoric Acid Ys a4 out 
Water ... * “ta. Eaoro 
100 
Tt is found at St. Agnes, in Cornwall, Bodennais, in the 
veins of gold mines of Véréspatak, in Transylvania, and in the 
United States. The fibrous varieties are found in basaltic lava 
in the Isle of France, near Kertsch, in the Crimea, and Mullica, 
in New Jersey. In peat swamps in the Shetland Islands. In 
the Isle of Man occurring with the horns of the elk and deer. 
Tt also occurs in clay, mud, and peat; and, as in the present 
example, upon fossil shells at Bowbridge, near Stroud, Glouces- 
tershire. 
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