Page 259 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

TABLE 7.1 CHARACTERISTICS OF SOME COPPER PHOSPHATE MINERALS

MINERAL FORMULA CRYSTAL COLOR MOHS
NAME SYSTEM HARDNESS

libethenite Cu 2 (P0 4 )(OH) orthorhombic light-to-dark 4
olive green
cornetite Cu 3 (P0 4 )(OH) 3 orthorhombic greenish blue 4.5
pseudomalachite Cu 5 (P0 4 ) 2 (OH) 4 monoclinic vitreous green 4.5-5
tagilite Cu 2 P0 4 (OH)-H 2 0 monoclinic vitreous green 4.5-5
ludjibaite Cu 5 (P0 4 ) 2 (OH) 4 triclinic vitreous blue green ?
sampleite NaCaCu 5 (P0 4 ) 4 Cl-5H 2 0 orthorhombic pearly light blue 4
zapatalite Cu 3 Al 4 (P0 4 ) 3 (OH) 9 -4H 2 0 tetragonal translucent pale 1.5
blue
hydrated synthetic Cu 3 (P0 4 ) 2 -xH 2 0 parameters not
basic phosphate known
turquoise CuAl 6 (P0 4 )(OH) 8 -4H 2 0 triclinic vitreous blue green 5-6
chalcosiderite CuFe 6(P0 4)(OH · 4 Η 2 0 triclinic vitreous light green 4.5
8
4
faustite (Zn, Cu)Al 6 (P0 4 ) 4 (OH) 8 · H 2 O triclinic waxy, dull apple 5.5
green

F I G U R E 7.1 Stability diagram for F I G U R E 7.2 Stability diagram for pseudo-
cornetite, pseudomalachite, libethenite, malachite, libethenite, and sampleite
and sampleite (after Pollard, Thomas, (after Pollard, Thomas, and Williams 1992b).
and Williams 1992b).