Merrifield, Mary P.: The art of fresco painting, as practised by the old Italian and Spanish masters, with a preliminary inquiry into the nature of the colours used in fresco painting: with observations and notes (London: Charles Gilpin, 1846)

xliv

OF THE COLOURS USED

copper and silver mines, and sometimes in gold mines, frequently
close together, and even adhering to the same piece of ore, and that
they were a certain criterion of the presence of copper. The fact is,
that they were all native carbonates of copper, changing their name
according to the prevalence of the blue, or green, or greenish-blue
colour. The first (Chrysocola) will again be noticed. The Armenian
Stone is by most writers described to be of a greenish blue colour,
and this corresponds, as I shall prove, with the Azul Verde of Palo-
mino, and the Verde Azzurro of the Italians. The Coerulea is the
native blue carbonate of copper, of which there are two species, the
earthy and the indurated; the last was frequently mistaken for the
Lapis Lazuli, from which ultramarine is prepared.
I shall give, concisely, Agricola’s description of the pigment he
calls Coeruleo. He says, (p. 219, 221) there were two kinds known in
his time, the native and the artificial; that the native was often
attached to the same ores as Chrysocola, namely, copper ores; that
it was found not only in copper mines, but in those of silver and
gold, and that it always shewed the presence of copper; that it was
brought from Spain, Germany, Noricum, Dacia, Rhsetia, &c., but
was scarce because the factitious was more in use. He adds
(p. 452), “now this is the Coeruleo which the vulgar call azzurro,
which, together with the Chrysocola, is attached to the ore,” (or
matrix). He says also, that it resembled a hard sand, and is scraped
off the ore like sand. And see also Matthioli (p. 1412), who agrees
in the general description. The mineral here described is clearly
the earthy blue carbonate of copper, of which the following descrip-
tion is given in the Encyc. Brit. Art. Mineralogy.
Subspecies I. Earthy Azure Copper Ore.—Exter. Char.
Rarely found massive, usually disseminated or superficial; composed
of fine particles, which are dull and somewhat coherent; fracture
earthy.
Colour, smalt blue, sometimes sky blue ; opaque ; stains a little ;
soft or friable.
The earthy variety is found in superficial layers on a slaty marl in
Hessia, and it is also found superficial on sandstone in Thuringia.
Sometimes the whole of the sandstone is impregnated with this
earthy carbonate of copper, there called copper sand earth or copper