Shattuckite
Shattuckite, Cu5(SiO3)4(OH)2, is deep to medium blue and silky: hardness about 3.5, density 4.11. Its Cu:Si ratio of 1.25 tops all five Cu–Si–O–H IMA rows.
Shattuckite is a copper silicate, Cu5(SiO3)4(OH)2 on the IMA list (Rd, 1967 s.p., USA), named for its type locality, the Shattuck mine at Bisbee, Arizona. It is deep to medium blue and silky, hardness about 3.5, density 4.11, so a 20.00 g piece reads 15.13 g in water. Its 5:4 copper-to-silicon ratio is the highest of the five IMA rows built only of Cu, Si, O and H.
In short
- The species. The Handbook of Mineralogy sheet gives Cu5(SiO3)4(OH)2, orthorhombic, rarely in prismatic crystals to 2 mm and typically as spherulitic masses of acicular crystals; cleavage perfect on {010} and {100}; hardness about 3.5; density 4.11; deep to medium blue and silky; biaxial (+). The September 2026 IMA-CNMNC Master List lists it as Rd, 1967 s.p., USA.
- The 1.25 line. A script over the IMA list finds 5 rows whose formula is built only of copper, silicon, oxygen and hydrogen: apachite, dioptase, gilalite, planchéite and shattuckite. Shattuckite’s Cu:Si is 1.25; planchéite and dioptase are 1.00, apachite 0.90, gilalite 0.83. Worked on standard atomic weights it also carries the most copper of the five, 48.43% by mass, and the least water-equivalent, 2.75%.
- Documented failure: an analysis alone. The planchéite sheet’s Mindouli analysis works out at Cu:Si 1.20, nearer shattuckite’s 1.25 than planchéite’s own 1.00, and the shattuckite sheet’s Ajo analysis had 0.58% quartz deducted. Evans and Mrose (1977) say the two are so similar in appearance that they have often been confused. Hardness (about 3.5 against 6) and weight in water (15.13 g against 14.52 to 14.74 g) separate them better.
- Where it is found. The sheet’s Distribution starts at the Shattuck mine, Bisbee, and runs through the New Cornelia mine at Ajo and other Arizona mines to Nevada, New Mexico and Sonora, Tsumeb, Tantara and M’Sesa near Kambove in the Katanga Copperbelt, and two Greek islands.
- Shattuckite or chrysocolla. The sheet names chrysocolla first among shattuckite’s associates. chrysocolla is 1.93 to 2.4, so a 20.00 g piece reads 9.64 to 11.67 g in water against shattuckite’s 15.13 g; the full separation is on shattuckite vs chrysocolla.
| Name | Formula (IMA), status | Cu:Si | Cu by mass | Water-equivalent | Hardness (sheet) | Density (sheet) | 20.00 g piece in water |
|---|---|---|---|---|---|---|---|
| Shattuckite | Cu5(SiO3)4(OH)2; Rd, 1967 s.p. | 1.25 | 48.43% | 2.75% | ~3.5 | 4.11 | 15.13 g |
| Planchéite | Cu8(Si4O11)2(OH)4·H2O; Rd, 1967 s.p. | 1.00 | 43.41% | 4.62% | 6 | 3.65–3.80 | 14.52–14.74 g |
| Dioptase | CuSiO3(H2O); G, 1798 | 1.00 | 40.31% | 11.43% | 5 | 3.28–3.35 | 13.90–14.03 g |
| Apachite | Cu9Si10O29·11H2O; A, 1979-022 | 0.90 | 37.75% | 13.08% | 2 | 2.80 | 12.86 g |
| Gilalite | Cu5Si6O17·7H2O; A, 1979-021 | 0.83 | 35.93% | 14.26% | 2 | 2.72 | 12.65 g |
| Chrysocolla (carries Al) | (Cu2-xAlx)H2-xSi2O5(OH)4·nH2O; A, 1980 s.p. | At most 1.00 (x = 0); 0.89 and 0.90 in the sheet analyses | 33.55% and 37.49% (sheet analyses) | 9.60% and 19.46% (sheet analyses) | ~2–4 | 1.93–2.4 | 9.64–11.67 g |
What is shattuckite? A copper silicate named for a Bisbee mine
Shattuckite is Cu5(SiO3)4(OH)2, an orthorhombic copper silicate of oxidised copper deposits. The Handbook of Mineralogy shattuckite sheet gives point group 2/m 2/m 2/m and space group Pcab: rarely as well-formed prismatic crystals to 2 mm, typically as aggregates of spherulitic masses composed of acicular crystals. Cleavage is perfect on {010} and {100}; hardness about 3.5; measured density 4.11 against a calculated 4.128. It is deep to medium blue, silky and semitransparent. The sheet prints no streak, and this page gives none.
Optics. Biaxial (+), α 1.753, β 1.782, γ 1.815, with a calculated 2V of 88°; worked from those indices the 2V is 87.8° and the birefringence 0.062. The sheet prints pleochroism X very pale blue, Y pale blue, Z deep blue. Evans and Mrose (1977), American Mineralogist 62, 491–502 report the opposite on clear single crystals: no appreciable pleochroism in shattuckite or planchéite, and they suggest that observations on aggregates or very thin fibres may have been misread. Both are printed here because both are published.
What the lists record. The September 2026 IMA list gives Cu5(SiO3)4(OH)2, status Rd, 1967 s.p., country USA, with Evans and Mrose 1977 as second reference. The sheet names it for the type locality, the Shattuck mine, Bisbee, Arizona, and places type material at the National Museum of Natural History, Washington. Evans and Mrose describe the structure as brucite-like (CuO2)n layers with pyroxene-type (SiO3)n chains joined to their surfaces; planchéite’s is very similar except that the pyroxene-type chains are replaced by amphibole-type chains.
How much copper is in shattuckite? The 1.25 line
Shattuckite has five copper atoms to four silicon, the highest ratio among the copper silicates built of nothing else. Method: a field scan of the September 2026 IMA list, cross-checked by a token scan of every line, kept rows whose formula contains copper and silicon and no element other than oxygen and hydrogen. Both scans return the same 5 rows: apachite, dioptase, gilalite, planchéite and shattuckite. Their Cu:Si ratios are, in that order, 0.90, 1.00, 0.83, 1.00 and 1.25.
Worked on standard atomic weights. Cu5(SiO3)4(OH)2 has a formula mass of 656.07 and is 48.43% copper; as oxides it is CuO 60.62%, SiO2 36.63% and H2O 2.75%, exactly the sheet’s ideal column. Planchéite is 43.41% copper, dioptase 40.31%, apachite 37.75% and gilalite 35.93%. The sheet’s Ajo analysis gives 48.26% copper and Cu:Si 1.244; the Mili, Evvia, microprobe analysis gives 47.13% and 1.198, with 1.6% MnO.
Where chrysocolla sits. Chrysocolla is not one of the five, because its IMA formula, (Cu2-xAlx)H2-xSi2O5(OH)4·nH2O, carries aluminium. On that formula its Cu:Si is (2 − x)/2, at most 1.00. The chrysocolla sheet’s two analyses work out at 0.89 and 0.90, with 33.55% and 37.49% copper. Density follows the same order in the table above, from shattuckite’s 4.11 down to chrysocolla’s 1.93 to 2.4; this page makes no claim about why.
Shattuckite or planchéite? Where the analysis fails
Documented failure: one analysis can sit closer to the wrong mineral. The Handbook planchéite sheet prints an analysis from Mindouli, Congo, of 59.20% CuO and 37.16% SiO2. Worked, that is Cu:Si 1.20, much nearer shattuckite’s 1.25 than the 1.00 of planchéite’s own ideal formula. The shattuckite sheet’s Ajo analysis was recalculated after deducting 0.58% quartz. Evans and Mrose (1977) write that the two are so similar in appearance that they have often been confused, and even said at times to be identical, and that their close association with each other and with chrysocolla and dioptase, and the difficulty of obtaining really pure bulk samples for analysis, long left their chemistry uncertain.
What does separate them, on the sheets. Hardness: about 3.5 against 6. Density: 4.11 against 3.65 to 3.80, so a 20.00 g piece reads 15.13 g in water as shattuckite and 14.52 to 14.74 g as planchéite, about 0.4 g apart at the nearest. Indices: shattuckite α 1.753 to γ 1.815, planchéite α 1.697 to γ 1.741. Colour, per Evans and Mrose: shattuckite deep blue to medium blue, planchéite light to very light greenish blue; the planchéite sheet itself allows pale blue to deep blue as well.
On a balance. The weighing method is on how to measure specific gravity at home and the scratch test on how to test mineral hardness properly. A deep blue silky crust that reads near 15.1 g for 20.00 g is the shattuckite reading; malachite is 15.06 g, so weight alone does not part those two, while malachite’s green colour and its carbonate formula do.
Where is shattuckite found?
The Distribution field, as printed. In the USA, in Arizona: the Shattuck mine, Bisbee, Cochise Co.; the New Cornelia mine, Ajo, Pima Co.; the San Manuel and Mammoth-St. Anthony mines, Tiger, Pinal Co.; the Clifton-Morenci district, Greenlee Co.; and several localities south of Wickenburg, Maricopa Co. The Santa Fe district, Mineral Co., Nevada, and the Buckhorn mine, Red Cloud district, Lincoln Co., New Mexico. Munihuaza, near Alamos, Sonora, Mexico. Tsumeb, Namibia. Tantara and M’Sesa, near Kambove, Katanga Province, Congo, on the Katanga Copperbelt page. Mili, Evvia Island, and Apikia, Andros Island, Greece. We add no other locality.
How it occurs. The sheet calls it a secondary mineral in oxidized copper deposits, and names its associates as chrysocolla, ajoite, malachite, quartz and hematite. Ajoite, another blue copper silicate, is the subject of is ajoite a quartz; the IMA list writes it K3Cu2+20Al3Si29O76(OH)16·8H2O, Cu:Si 0.69.
The rest. Shattuckite is a copper compound; for handling questions see toxic minerals in a collection, HSE EH40, COSHH 2002 or a clinician: this page is not advice. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.