There is also another proof of minerals, which is without Lead, with Venice, or any other good fusible glass, where one or two ounces of the powdered mineral are mixed with half an ounce of the powdered glass, and being mixed and covered in a crucible, are melted, and poured out; by which means the glass attracts, and dissolves that mineral, and is thereby coloured, which shews what metal is contained in the mine, after which may be made another tryal by Lead, tryal being first made by the first proof. And this is the fittest proof for the hardest minerals, which are even invincible, as are the _Lapis hemititis_, _smiris_, granats, talck black and red, and those which abound oftentimes with gold, and silver, which because they cannot be mixed with Lead are not esteemed, but are oftentimes cast away, although they abound with gold and silver, and this because they cannot be tryed, Which being tryed after the aforesaid manner, and consequently the treasures lying therein being discovered, thou mayst afterward with more confidence handle them, and reduce them to better profit. Now those colours which follow, indicate the tenure of them. Glass resembling the greenness of the Sea signifies meer Copper, but the greenness of grass, signifys copper, and iron mixed together: glass of a rusty colour signifys iron: yellowish glass signfys tin, glass of a yellow golden colour, or like a red ruby signifys silver: Blew glass like a saphir signifys pure gold; a smaragdine signifys gold mixed with silver: An Amethyst colour signifys gold, silver, copper, and iron mixed together. Besides these, glass sometimes gets other colours, according to the diversity of the weight of divers metals mixed together; which use will teach with a further practise that is to be made with Saturn.