314 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



VESUVIANITE (393) 



IDOCRASE 



Basic silicate of lime and alumina, in 

 part represented by the formula 

 2H 2 0. 12CaO. 3(A1, Fe) 2 O 3 .10SiO 2 . 

 Boron is often present in small 

 amount. Tetragonal. 



Vesuvianite has been reported from only a few localities in Idaho, 

 where it has been collected in association with ore minerals. None 

 of the specimens seen are good mineralogical specimens of the 

 mineral, although a careful search of the localities might obtain 

 cabinet specimens. Vesuvianite, like epidote, lime garnets, etc., 

 is a mineral commonly found in metamorphosed limestone. 



BLAINE COUNTY 



Vesuvianite occurs as hair-brown long prismatic crystals in 

 wollastonite in a specimen from the Starlight mine in Elkhorn 

 Gulch near Ketchum in the Warm Springs district, Hailey quad- 

 rangle. The crystals are deeply striated vertically and reach a 

 length of 15 mm. But few of them are terminated. One which 

 was measured gave the following angles: 



Measurements of vesuvianite crystal, Starlight mine 



The habit, as will be seen from the drawing, (fig. 80) is prismatic 

 and very simple. 



CUSTER COUNTY 



Umpleby 39 found vesuvianite in the No. 4 crosscut of the Alberta 

 tunnel, Alder Creek district, where it occurred as bunches of acicular 

 radiating crystals which replace dull-gray manganese stained lime- 

 stone. The largest bunches are 15 mm. in diameter. Another 

 specimen labeled " Actinolite in garnet rock from 100 feet in Alberta 

 No. 4," which is stated to be abundant here, consists of vesuvianite 

 forming a streak 1 cm. wide and several centimeters long in dense 

 brown garnet rock. The vesuvianite is greenish-brown in color and 

 acicular in structure, being made up of close packed elongated 



»' J. B. Umpleby. U. S. Geol. Surv., Prof. Paper 97, p. 55, 1917. 



