Siliceous Sinter of the Azores. 391 
55. Siliceous Sinter of the Azores. 
Mr. SILuiman, 
In examining some varieties of siliceous sinter from the 
Azores, I have met with one which differs from any hither- 
to found in Iceland or other countries, ag the substance 
occurs under those forms usually seen in our cabinets 
From the island where this variety occurs (St. Michaels) it 
might perhaps be distinguished by the term Michaelite. 
From the specimens_ before me I send you the following 
description. — four’ ae ie: 
Sy es : a WEBSTER. 
External Characters. ~ z pee 
Color snow white, reddish and yellowish white, passing 
in some specimens to yellowish grey. 
It oceurs in ae slender (capillary) filaments, from one 
to four inches in 
The filaments cross each other in every direction. 
On the cross kag Se viewed with a microscope, a aa 
pata vitreous and pearly is observed. — 
tis nes 
bins gravity 1.866. 
Chemical Characters. 
Infusible without sisting before Brooke’s sessed 
Sir grains in fife ieee intensely ged in a platina 
crucible for fifteen minutes, lost 0.98125 grains, equal to 
16.35 per cent. 5, itis an hydrate ofl and is composed of 
Silex 
Water, - -~ 16.35 
