A metallic globule with or without an incrustation may be obtained.
Gold and copper salts give a metallic bead without an incrustation.
All the large and some of the small islands appear to be composed of ancient volcanic rock, with an incrustation of coral limestone showing here and there along the coast.
Cadmium salts can be recognized by the brown incrustation which is formed when they are heated on charcoal in the oxidizing flame of the blowpipe; and also by the yellow precipitate formed when sulphuretted hydrogen is passed though their acidified solutions.
On the top is a shallow cup for the reception of the one or two eggs, which have a bluish-white shell with chalky incrustation.