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And the Star does not diſſolve or efferveſce with Acids: In theſe Things the two approach to the new Stone; but neither can be allowed the ſame.
The green owes its Colour, moſtly, to Iron.I am convinced that ſome of this Stone contains that Metal; but not all; and that the Iron, where it is found, is no Eſſential Part of the Body; but a mere accidental Mixture: For I have Pieces from Sweden, which, tho' very green, do not become red in burning; and other green Pieces that acquire that Redneſs, which appears after burning in all Foſſils that have Iron in them.
The yellow holds a little Lead.
The blue does not owe its Colour to Copper; as is true alſo of the Lapis Lazuli; which is a Zeolite; and therefore allied to this Stone.
Of whatſoever Colour this Stone be, if carefully warmed, it has the electric Quality; leſs than the Tourmatine; but like it;
It has not the double Refraction of Spar; though it has much of its external Aſpect.
From theſe palpable Qualities; and certain Characters; we may advance toward an Enquiry into what it is.
The Mineral Acid, every where preſent in the Earth, (tho' never ſeen unmixed, or in its pure, ſimple ſtate) when joined with Metals, we ſee, forms the Vitriols; when united with Clay it makes the Alums; when mixed with
