BULLETIN 118, UNITED STATES NATIONAL MUSEUM. 



Metals forming the bases of precious stones. 



Aluminum Al 



Barium Ba 



Beryllium (or glucinum) Be 



Calcium Ca 



Cerium Ce 



Chromium Cr 



Cobalt Co 



Copper (cuprum) Cu 



Hydrogen H 



Iron (ferrum) Fe 



Lead (plumbum) Pb 



Lithium Li 



Magnesium Mg 



Manganese Mn 



Mercury (hydrargyrum) Hg 



Nickel Ni 



Potassium (kalium) K 



Sodium (natrium) Na 



Tin (stannum) Sn 



Titanium Ti 



Uranium U 



Vanadium V 



Yttrium Y 



Zinc Zn 



Zirconium Zr 



Nonmetals forming the acid portions of precious stones. 



Boron B 



Carbon C 



Chlorine CI 



Columbium Cb 



Fluorine F 



Oxygen O 



Phosphorus P 



Silicon Si 



Sulphur S 



( 'nj sterilization. — When a chemical compound passes from the 

 liquid or gaseous state into the solid condition, cohesion and chemi- 

 cal affinity tend to draw its atoms together, and if these become 

 grouped in a regular manner solids bounded by plane surfaces result; 

 these are known as crystals. Six crystal systems (one of them 

 consisting of two subsystems) are recognized, as follows: 1, Isometric, 

 or cubic, comprising those crystals developed exactly alike in the six 

 directions in space (front, back, right, left, up, and down), at right 

 angles to one another; these have the general aspect of spheres, 

 regularly flattened at an even number of equal intervals, and in- 

 clude the cube, regular octahedron, rhombic dodecahedron, etc., 

 as well as combinations of these simple forms. 2, Tetragonal, 

 comprising those crystals developed according to two different 

 patterns, one repeated four times in directions at equal intervals in 

 a plane, the other twice in the directions at right angles to that 

 plane, all being at right angles to one another. The crystals of this 

 system are made up of pinacoids, prisms, and pyramids. 3, Hexag- 

 onal, comprising crystals developed according to two different pat- 

 terns, one repeated six times in directions at intervals lying 60° 

 apart in a plane, and the other twice in the directions at right angles 

 to that plane; the forms are like those of the tetragonal system. 

 Trigonal (a subsystem of the hexagonal), comprising crystals devel- 

 oped according to two different patterns, one repeated three times 

 at intervals lying 120° apart in a plane, and the other twice in the 

 directions at right angles to that plane. 4, Orthorhombic system 

 comprising those crystals developed according to three different 



