To the eighth genus of non aluminous silicates belong the species—
1st. Of the silicate of zirconia : amongst its varieties are :
1. The jacinth. | 3. The essonite.
2. The jargoon. |
2nd. Of the silicate of magnesia : amongst its varieties are :
1. The chrysolite. 4. The spuma marina,
2. The olivina. or sea froth.
3. The peridot.
To the ninth genus of united silicates and other composites belong the species—
1st. Of the fluoriferous silicates : amongst its varieties is found :
The topaz.
2nd. Of the sulphuric silicate : amongst its varieties are found :
1. The lapis-lazuli. | 2. The lazulite.
