2nd. Of the aluminous silicate of magnesia : some of its varieties are :
1. The dicroite. | 2. The hypersthenum.
3rd. Of the aluminous silicate of glucine: some of its varieties are :
1. The beryl. 3. The aquamarine of
2. The emerald. Ceylon.
| 4. The prasina.
4th. Of the aluminous silicate of soda: one of its varieties is :
Natrolite.
5th. Of the aluminous silicate of lime or of magnesia : amongst its varieties are :
1. The idocrasium. 4. The touchstone.
2. The pyroxenum. 5. The epidoto.
3. The schists.
6th. Of the aluminous silicate of lithia, of magnesia or lime : amongst its varieties are :
1. Mica. | 2. Lepidolite.
