ARGILLA (argillaceous earth) intimately united with leſs than half its weight of ſiliceous earth, and a ſmall quantity of mild calcareous earth.
Cronſtedt Min. §§ 43–48. Gemma.
The Gems ſuffer no change under the blowpipe, with foſſil fixed alkaly, but are diſſolved by microcoſmic ſalt and borax.
| To this head belong | Rubinus, the | ruby; |
| Saphirus, | ſapphire; | |
| Topazius, | topaz; | |
| Smaragdus, | emerald. |
The tourmaline holds a kind of middle place betwixt the gems and the ſcherle. The colour, in all of them, is owing to iron.
ARGILLA (argillaceous earth) intimately united to half its weight of ſiliceous earth (or more), and a little mild calcareous earth. Scherle.
Cronſtedt Min. §§ 68–71. Granatus et Baſaltes, which I call Scherle.
The remote varieties of theſe are eaſily diſtinguiſhed, the near ones difficultly.