458 W. T. BRIGIIAM ON THE VOLCANIC PHENOMENA 



crystals form over and conceal the former. The temperature of the caves where the gypsum 

 is deposited is not high, as will be seen in the description of the stalactitic formations farther 

 on. 



No beds of gypsum have been found in the upraised coral reef, and there does not seem 

 to have been any submarine emission of sulphur vapors to produce this deposit. 



Specimens of the gypsum-coated tubes of both varieties have been deposited in the 

 Museum of the Society. 



Cyanosite. 



An impure sulphate of copper is sometimes, though rarely, found in the sulphur beds of 

 Kilauea. An analysis, given in the Geological Report of the United States Exploring 

 Expedition, is as follows : — 



HOS0 3 NaO CuO Al+Fe Mn K CI Si 3 (insol.) Si and loss. 



37.97 16.80 10.80 5.0 4.0 trace 21.00 4.43 = 100.00 



Soda Alum — Solfatarite. 

 A strongly ferruginous soda alum is found in the smoking cones (fumaroles) in Kilauea. 



Halotrichite. 

 As the fibrous silky mass of the alum often contains little soda, it seems to run into 

 halotrichite. The free sulphuric acid in this mineral is often quite perceptible, and wholly 

 destroys the paper in which it is placed for a few days. 



Copperas. 

 It is found in the sulphur bank on the southern edge of Kilauea ; it is quite impure, and 

 from its solubility is usually dissolved as soon as formed, and is absorbed into the porous 

 earth resulting from the decomposition of the lava rock. 



Glauber Salt. 

 At Kailua, on the western shores of Hawaii, this mineral was abundant twenty years 

 since, forming in a cavern on the shore by the action of hot sulphurous gases on sea-water. 

 These gases have ceased to flow, and the springs are no longer hot. I did not visit the 

 place, but was told that no sulphate of soda was now found there. In Kilauea it is not 

 uncommon as a deposit on the under-surfice of lava crusts, and contains a little sulphate of 

 lime and sulphate of iron. 



Nitre. 



Found in small quantities in Kilauea on a ledge in a cave, in delicate acicular crystals. 

 The rock on which it was found was too porous to hold water, and the crystals must have 

 formed from a vaporous solution, or grown from the saturated rock. 



Calcite. 

 The chief deposits of carbonate of lime on the Hawaiian Islands are the extensive coral 

 beds. These are often very compact and solid, often baked by lava-streams to a compact 

 limestone, and ringing when struck. Where the lava has broken through the raised coral 

 reef, as in the shore craters of Oahu, the particles of coral are carried up with the tufa, and 

 may be found imbedded in an almost unaltered condition. It is usually, however, acted 

 upon by heat and sulphurous gases forming gypsum and aragonite. As a white incrustation 



