Is ajoite a quartz?
No. Ajoite is a hydrous potassium copper aluminium silicate, 40.63% CuO; quartz is SiO2, hardness 7. Its first analysis held quartz, caught by one X-ray line.
No. Ajoite is a hydrous potassium copper aluminium silicate, K3Cu20Al3Si29O76(OH)16·8H2O on the IMA list (approved 1958): 40.63% CuO by mass, bluish green, density 2.96. Quartz is SiO2, hardness 7, density 2.65, with no copper. They grow together: ajoite’s first analysis, from Ajo, Arizona, contained quartz, caught by its 3.34 Å X-ray line.
In short
- The verdict. The September 2026 IMA-CNMNC Master List gives ajoite its own row, K3Cu2+20Al3Si29O76(OH)16·8H2O, A, 1958, USA, and quartz another, SiO2. Pluth and Smith, PNAS 99, 11002 (2002), abstract describes ajoite as triclinic, a zeolitic framework of CuO6 layers and aluminosilicate layers with channels holding potassium, sodium and water. quartz is hexagonal SiO2 on its Handbook of Mineralogy sheet.
- The 3.34 Å line. Chao, American Mineralogist 66, 201 (1981) found the 1958 type pattern’s second-strongest line, 3.34 Å at 25 on a scale of 100, to be the quartz reflection, and judged the 1958 analysis and formula likely to be erroneous. Quartz’s Handbook pattern leads with 3.342 at 100. The two minerals were mixed in the first sample described.
- Documented failure: silica cannot prove the quartz. The 1958 analysis has 45.90% SiO2 and Chao’s 41.2%, 4.70 points apart. But the current IMA formula works out at 44.50%, nearer the 1958 figure than Chao’s ideal, 41.48%. A silica percentage alone did not show the contamination; the X-ray line did.
- Choose the reading by what you have. Weight on a clean piece: 13.24 g in water for 20.00 g at ajoite’s 2.96, 12.45 g as quartz at 2.65. Refractive index: ajoite α 1.550 to 1.565, γ 1.641 to 1.650; quartz 1.544 and 1.553. Birefringence 0.085 to 0.091 against 0.009. An inclusion inside quartz gives the quartz reading.
- Ajoite in quartz. A label of that kind names two minerals, the host and the inclusion; how the term is used is on what is a phantom crystal. The papagoite sheet records papagoite included in quartz crystals at Messina, South Africa, with quartz and ajoite as its associates there. This page found no fetched source describing the ajoite inclusions themselves, so it says no more.
| Reading | Ajoite | Quartz | Papagoite | Shattuckite | Chrysocolla | Does it separate ajoite from quartz? |
|---|---|---|---|---|---|---|
| IMA formula | K3Cu2+20Al3Si29O76(OH)16·8H2O | SiO2 | CaCuAlSi2O6(OH)3 | Cu5(SiO3)4(OH)2 | (Cu2-xAlx)H2-xSi2O5(OH)4·nH2O | Yes |
| CuO, wt% | 40.63 (IMA formula); 42.2 (Chao analysis) | 0 | 23.53 (sheet analysis) | 60.41 (sheet analysis 1) | 42.00 to 46.93 (sheet analyses) | Yes, with an analysis |
| SiO2, wt% | 44.50 (IMA formula); 45.90 (1958); 41.2 (1981) | 100 | 33.60 | 36.68 | 35.80 to 39.48 | Yes; but the 45.90 held quartz |
| Strongest X-ray lines, Å | 12.4 (100); 3.34 (25) in 1958, the quartz line per Chao | 3.342 (100) | 2.874 (100) | 4.42 (100) | 1.486 (100) | Yes: 3.34 Å flags quartz |
| Density | 2.96 (1958); 2.951 calc. (1981) | 2.65; 2.59 to 2.63 massive | 3.25 | 4.11 | 1.93 to 2.4 | Yes, on a clean piece |
| 20.00 g in water | 13.24 g | 12.45 g | 13.85 g | 15.13 g | 9.64 to 11.67 g | Yes, 0.79 g; not for an inclusion |
| Refractive indices | α 1.550 to 1.565; γ 1.641 to 1.650 | ω 1.544; ε 1.553 | α 1.607; γ 1.672 | α 1.753; γ 1.815 | α 1.575 to 1.585; γ 1.598 to 1.635 | Yes, on a polished face |
| Birefringence, worked | 0.085 (1958); 0.091 (1981) | 0.009 | 0.065 | 0.062 | Up to 0.060 | Yes |
| System | Triclinic (Chao; Pluth and Smith) | Hexagonal | Monoclinic | Orthorhombic | Orthorhombic (?) | Yes, by X-ray |
| Colour | Bluish green (1958, 1981) | Colourless, white; blue among many | Cerulean blue | Deep to medium blue | Blue, blue-green, green | No |
| Hardness | Not printed in the fetched sources | 7 | 5 to 5.5 | About 3.5 | About 2 to 4 | Not quotable for ajoite |
Is ajoite a type of quartz?
No: it is a separate mineral species with copper, aluminium and potassium in it. The September 2026 IMA list writes ajoite K3Cu2+20Al3Si29O76(OH)16·8H2O, status A, 1958, USA, citing American Mineralogist 43 (1958), 1107. Quartz is SiO2, one of 8 IMA rows with that formula. Worked on standard atomic weights, ajoite’s formula is 40.63% CuO, 44.50% SiO2, 3.91% Al2O3, 3.61% K2O and 7.36% H2O; quartz is all silica. The mineral-definition test is on is quartz a mineral and is not repeated here.
Its structure is not quartz’s. Pluth and Smith, PNAS 99, 11002 (2002), abstract solved the structure on a crystal from the type locality: triclinic, a zeolitic octahedral–tetrahedral framework of edge-sharing CuO6 layers and curved aluminosilicate layers and strings, with channels of 12- and 8-rings of tetrahedra holding potassium, sodium and water. Chao (1981) had already shown it triclinic, not monoclinic as first thought.
Why did the first ajoite analysis contain quartz?
Because the type material is intergrown with it. Schaller and Vlisidis, American Mineralogist 43, 1107 (1958) named ajoite after Ajo, Pima County, Arizona, from specimens collected by Harry Berman in August 1941. They describe most of it as compact and massive, intimately mixed with dark blue shattuckite and white massive quartz, and they hand-picked out shattuckite before analysis. Their sample had a pycnometer specific gravity of 2.96.
The 3.34 Å line. Chao, American Mineralogist 66, 201 (1981), working on New Cornelia mine material from Ajo, wrote that the 1958 powder data indicated a significant amount of quartz in the analysed material, the 3.34 Å quartz reflection being the second strongest line with an intensity of 25 on a scale of 100, and that the reported analysis and formula were therefore likely to be erroneous. Quartz’s Handbook pattern is led by 3.342 at 100. Chao’s ideal was (K,Na)Cu7AlSi9O24(OH)6·3H2O; the IMA formula has the atom counts of the 2002 structure formula, (K + Na)3Cu20Al3Si29O76(OH)16·~8H2O, with potassium written for K + Na.
The documented failure. It would be natural to expect the quartz to show as extra silica. It does not, cleanly: the 1958 analysis has 45.90% SiO2, Chao’s 41.2%, and the IMA formula 44.50%. A silica figure sits between the two analyses and proves nothing on its own; the X-ray line was the evidence.
How do you tell ajoite from quartz and the blue copper silicates?
On a loose, clean piece, weigh it. Worked as 20 − 20/D, 20.00 g reads 13.24 g in water at ajoite’s 2.96 and 12.45 g as quartz at 2.65, 0.79 g apart; the method is on how to measure specific gravity at home. Papagoite reads 13.85 g, shattuckite 15.13 g, and chrysocolla 9.64 to 11.67 g on their sheets.
On a polished face, the refractometer. Ajoite’s indices run α 1.550 (1981) to 1.565 (1958) and γ 1.641 to 1.650, a birefringence of 0.085 to 0.091. Quartz reads ω 1.544 and ε 1.553, 0.009. The separation of shattuckite from chrysocolla is on shattuckite vs chrysocolla.
Where both fail. Colour does not separate them: ajoite is bluish green, papagoite cerulean blue, shattuckite deep to medium blue, chrysocolla blue to green. An ajoite inclusion inside a quartz crystal gives quartz’s weight and quartz’s indices, because the host is what you measure. No fetched source here prints a hardness for ajoite, so this page gives none.
What does ajoite in quartz mean on a label?
Two minerals in one specimen. As with the other is-it-a-quartz questions on this site, is celestite a quartz, is chalcedony quartz, is aventurine a quartz and is dumortierite quartz, the word quartz on such a label names the host. The included mineral keeps its own name and formula. What an included zone or phantom is, and how to read one, is on what is a phantom crystal.
What the sheets do say about Messina. The Handbook of Mineralogy papagoite sheet prints papagoite as sheets and rings of microcrystalline radiating aggregates enclosed in quartz crystals, gives its occurrence as included in quartz crystals at Messina, South Africa, and names quartz and ajoite as its associates there. So two blue copper silicates are recorded together with quartz at Messina, and colour will not say which one a blue inclusion is: papagoite is cerulean blue, ajoite bluish green.
What this page could not source. Searches for ajoite in quartz returned dealer and auction listings, and Mindat refused the fetch. No museum, survey or peer-reviewed description of the ajoite inclusions themselves was found, so this page says nothing about their habit or how they formed. A blue inclusion is identified by analysis.
Related pages are under the collecting guides. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.