86 University Geological Survey of Kansas. 
Fic. 6. Iie, 7 Fic. &. Fie. 9. 
Figure 6. Form of gypsum crystal. 
Figure 7. Common form of gypsum crystal. 
Figure 8. Twinned gypsum crystal. 
Figure 9. Twinned gypsum crystal, with edges rounded — Monte Marte twin. 
of the crystals near Monte Marte, near Paris, and so these crys- 
tals are sometimes called the Monte Marte twins. 
Gypsum is only slightly soluble in water, as shown in the 
following table of Marignac: 
Solubility of Gypsum, by Marignac.® 
One part gypsum dis- One part anhydrous 
Temperature. solves in— sulphate lime dis- 
solves in— 
AN BP” IN —AOP (O55 co00 Cb0d Dow 0000 415 parts of water...... 525 parts of water. 
Ih Chea 1) adi Osis goooadoaccadée aiono) pO Behe: sees Anolon re 
JNi6 CD74 LO oS (Cs oc 06 soso 0000 Bite) 1 Mt Pesyeeie ta AO ian cs es 
AMG SDA? SB” Ol scoogoscagoaeoss adh SS eid gates cpa 470 te 
AG AKO OL4E leh esis Oo gaasadgooacecde ale) OO Gea N eam Ako), is 
ANG MOB for pS (Os nc00 bb00 bo odo0 a). Create tee 468 15s a0 
AMG WAGE es Oo ooo aiooaced one aa) 08 eae a iok 474“ oe 
AMG UGG? I 2 (Osossooocodcctes ah OG patentee 495“ te 
AMG USO IMea=O Co ogacdesoeac000 ATS *f scale, RE Meat aye) | a 
INTRON De OOS (Olid oy, heb asl, oot 452 «6 Cire eh 5712“ 6 
The maximum solubility is found at 38°C. or 100°F., and 
then only one part of gypsum dissolves in 368 parts of water, 
while about 40 parts of common salt will dissolve in 100 parts 
of water at a temperature of 60°F. 
38. Annales de Chimie, Paris. 5th series, vol. 1, pp. 274 to 281, quoted by Chatard, Seventh An-., 
nual U.S. Geol. Survey, and verified by the writer. 
