GYPSUM. 457 



material by persons not acquainted with the two minerals. This form of 

 gypsum was used in ancient times for window glasses. It is said that Nero's 

 house at Rome had windows of this material which had the peculiar quality 

 of permitting things to be seen without from within, but did not permit things 

 to be seen in the house from the outside. This form is found in many places, 

 but generally in small crystals. At the head of Canal Creek, in Hardeman 

 County, and not far west of the Eight Ranch, in King County, are some fine 

 crystals. It is very easily distinguished from isinglass or mica by heating it. 

 If it is gypsum it turns white at once and falls to pieces, while mica is not 

 affected by heat. 



Radiate. — Is a kind of gypsum that has a radiated structure. It occurs 

 in round bails in places, having great specific gravity. 



Fibrous. — This variety is also known as Satin Spar. It occurs in white or 

 delicately tinged fibrous masses. It occurs in beds of the red clay in seams 

 traversing the clay in various directions. It seems to have been formed by 

 precipitation in cracks in the clay, crystalizing from the centre outward. 

 Very few of the seams are more than two inches thick. At one place in 

 Kent County, near the Salt Fork of the Brazos, I found a seam twelve inches 

 thick. This is the thickest seam I have seen in the formation of this form of 

 gypsum. 



Alabaster. — A compact snowy variety, sometimes tinged with various 

 colors. It is cut into vases and ornaments, and receives a fine polish; it 

 owes its beauty to its color and translucent structure. It is found in many 

 places along the Salt Fork of the Brazos and other localities throughout the 

 gypsum belt. 



Rose G-ypsum. — A peculiarly beautiful form of gypsum at Sweetwater, in 

 Nolan County. It is called by the people there u petrified roses." It is a 

 peculiar form of selenite in rounded masses of thin rose-like leaves that 

 give it the appearance of roses. These masses are colored red by the clay 

 and iron, and when freed from the surrounding clay are very beautiful, and 

 make excellent and beautiful specimens for the cabinet. 



Massive. — The greater part of the gypsum in the district is the heavy- 

 bedded, massive white and bluish beds. They occur in beds of various 

 thickness. There is also a great deal of gypsiferous marls and clays, as well 

 as heavy beds of gypseous sandstones. 



A few sections from different localities will give an idea of the quantity of 

 gypsum to be found in this district and its mode of occurrence. The follow- 

 ing is a section of Kiowa Peak, in the northeastern corner of Stonewall 

 County, beginning at the bottom: 



