Papagoite
Papagoite, CaCuAlSi2O6(OH)3: cerulean blue monoclinic copper silicate, hardness 5 to 5.5, density 3.25, from Ajo, Arizona, and in quartz crystals at Messina.
Papagoite is a calcium copper aluminium silicate, CaCuAlSi2O6(OH)3 on the IMA list: cerulean blue, monoclinic, in crystals to 3 mm, hardness 5 to 5.5, density 3.25. Its Handbook sheet records it in veinlets at the New Cornelia mine, Ajo, Arizona, and included in quartz crystals at Messina, South Africa, with ajoite as an associate there.
In short
- The formula. The September 2026 IMA-CNMNC Master List writes CaCuAlSi2O6(OH)3, status A, 1962 s.p., USA, with the 1960 description in American Mineralogist and Groat and Hawthorne’s 1987 structure refinement as references. The Handbook of Mineralogy sheet prints the same. Worked on standard atomic weights, it is SiO2 36.00, Al2O3 15.27, CuO 23.83, CaO 16.80 and H2O 8.10 by mass.
- The Ajo analysis check. The sheet prints one analysis, from Ajo, and a formula derived from it. Recast by script, copper and calcium reproduce: Cu:Si 0.529 and Ca:Si 0.543 against the printed 0.529 and 0.545. Aluminium does not: 0.553 against 0.524. The printed 15.78% Al2O3 would need to be 14.94% to give the printed ratio.
- Documented failure: the 3.25 check. The sheet’s cell, a 12.926, b 11.496, c 4.696 Å, β 100.81°, Z = 4, holds 685.4 ų. With the IMA formula that gives 3.235, which rounds to 3.24, not the printed calculated 3.25; the sheet’s own empirical formula gives 3.215. The measured 3.25 is 0.015 above the ideal figure.
- Papagoite in quartz. The sheet records sheets and rings of microcrystalline radiating aggregates enclosed in quartz crystals, and gives its occurrence at Messina, South Africa, as included in quartz crystals, with quartz and ajoite as associates. Telling the two blue copper silicates apart is on papagoite vs ajoite; the quartz question is on is ajoite a quartz.
| Quantity | IMA formula, worked | Ajo analysis, as printed | Difference | Recast by script | Printed formula | Reproduces? |
|---|---|---|---|---|---|---|
| SiO2, wt% | 36.00 | 33.60 | −2.40 | — | Si 1.87 | — |
| Al2O3, wt% | 15.27 | 15.78 | +0.51 | — | Al 0.98 | — |
| CuO, wt% | 23.83 | 23.53 | −0.30 | — | Cu 0.99 | — |
| CaO, wt% | 16.80 | 17.02 | +0.22 | — | Ca 1.02 | — |
| H2O, wt% | 8.10 | 9.01 (H2O+), 0.04 (H2O−) | +0.91 | — | (OH)3.04 | — |
| Cu:Si | 0.500 | — | — | 0.529 | 0.529 | Yes |
| Ca:Si | 0.500 | — | — | 0.543 | 0.545 | Yes, within 0.003 |
| Al:Si | 0.500 | — | — | 0.553 | 0.524 | No: needs 14.94% Al2O3 |
| Calculated density on the sheet’s cell (Z = 4) | 3.235 | Measured 3.25 | — | 3.215 (printed empirical formula) | Printed calc. 3.25 | No: 3.24 at best |
What is papagoite? A calcium copper aluminium silicate
CaCuAlSi2O6(OH)3, on the IMA list and on its sheet alike. The September 2026 IMA row is status A, 1962 s.p., country USA, citing American Mineralogist 45 (1960), 599, the description by Hutton and Vlisidis titled as from Ajo, Arizona, and Mineralogy and Petrology 37 (1987), 89, Groat and Hawthorne’s refinement of the structure. The formula mass is 333.79 on standard atomic weights.
What the sheet records. The Handbook of Mineralogy papagoite sheet gives monoclinic, point group 2/m, space group C2/m. Equant crystals to 3 mm, slightly flattened on {001}, with the faces in the [010] zone well developed and striated; also sheets and rings of microcrystalline radiating aggregates enclosed in quartz crystals, and massive veneers. Cleavage distinct on {100}, noted in thin section. Hardness 5 to 5.5. Density 3.25 measured and calculated. Cerulean blue, vitreous, translucent to transparent. Biaxial (−), α 1.607, β 1.641, γ 1.672, 2V 78°, so a birefringence of 0.065. Pleochroic: X colourless to very pale greenish blue, Y blue, Z deep greenish blue.
Name. For the Tohono O’odham, formerly called the Papago, who inhabit the region around Ajo, Arizona, as the sheet puts it.
What does papagoite in quartz mean?
Papagoite enclosed in quartz crystals, in the sheet’s words. Its habit line includes sheets and rings of microcrystalline radiating aggregates enclosed in quartz crystals; its occurrence line reads in narrow veinlets in altered granodiorite porphyry at Ajo, Arizona, and included in quartz crystals at Messina, South Africa. At Messina its associates are quartz and ajoite. A label reading papagoite in quartz names two minerals: the quartz host and the papagoite inside it.
What that means for measurement. Weighing or a refractometer reading on such a piece measures the host. A 20.00 g piece of papagoite alone would read 13.85 g in water at 3.25; quartz reads 12.45 g at 2.65. How included zones are read is on what is a phantom crystal. This page found no fetched source describing the Messina inclusions beyond the sheet’s two lines, so it says no more about them. Separating papagoite from ajoite, its blue-green associate there, is on papagoite vs ajoite.
Does the sheet’s analysis give its formula? The Ajo analysis check
Copper and calcium do; aluminium does not. The sheet prints one analysis, from Ajo: SiO2 33.60, TiO2 0.26, Al2O3 15.78, FeO 0.27, MnO 0.10, CuO 23.53, MgO 0.09, CaO 17.02, H2O+ 9.01, H2O− 0.04, total 99.70. It says this corresponds to Ca1.02Cu0.99Mg0.01Fe2+0.01Ti0.01Al0.98Si1.87O6(OH)3.04. Ratios to silicon do not depend on how the formula is normalised, so a script compares those. Cu:Si comes out 0.529, exactly the printed 0.99/1.87. Ca:Si is 0.543 against 0.545. Al:Si is 0.553 against 0.524; to give the printed ratio the analysis would need 14.94% Al2O3, not 15.78%.
What it does show. Against the IMA formula the analysis is 2.40 points short in silica and 0.91 over in water, and the printed formula has 1.87 silicon where the ideal has 2. Calcium and copper are the closest of the major oxides, 0.22 and 0.30 points from ideal. This page does not guess at the cause of the aluminium mismatch; it records that the printed formula does not follow from the printed oxides for that one element.
The 3.25 check: a calculated density that does not reproduce
The sheet’s cell gives 3.24, not 3.25. Monoclinic, a 12.926 Å, b 11.496 Å, c 4.696 Å, β 100.81°, so V = abc sin β = 685.4 ų. Four formula units of CaCuAlSi2O6(OH)3, 333.79 each, give a calculated density of 3.235. The sheet’s own empirical formula from the Ajo analysis gives 3.215. The sheet prints D(calc.) 3.25 beside a measured 3.25; the calculation as published here falls 0.015 to 0.035 short.
Why it matters little in the hand. At 3.235 or 3.25 a 20.00 g piece reads 13.82 or 13.85 g in water; a difference of 0.03 g. It matters for anyone checking the sheet, which is the point of recording it. The other blue copper silicates are compared on shattuckite vs chrysocolla and on the shattuckite and chrysocolla pages.
Where is papagoite found? The sheet’s localities
Distribution, as printed. In the New Cornelia mine, Ajo, Pima Co., Arizona, USA. In South Africa, from Messina, Transvaal. At the Sinclair mine, near Lüderitz, Namibia. The sheet marks no type locality and gives the type material as n.d.; the IMA list gives the USA, and the 1960 description is titled as from Ajo, Arizona. The term is explained on what is a type locality.
Associates, as printed. At Ajo: aurichalcite, shattuckite, ajoite and barite (baryte on this site). At Messina: quartz and ajoite. Copper-mineral hazard questions go to toxic minerals in a collection; this is not advice. More species are at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.