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466 APPENDIX. Order 111.—Infusible before Ike blowpipe. 1. Hardness equal or superior to that of quartz. Flint. 2. Scratch glass ; sometimes yield to the knife. Opal. 3. Yield to the knife. Serpentine.' 4. Yield to the nail. Mountain-cork. Class IV Saline Minerals. Soluble in Water; Sapid. Order I.—Afford a precipitate with carbonated alkali. Blue Vitriol. Order II.—Do not afford a precipitate with carbonated al< kali. Natron. HAUY’«