Is spodumene a pyroxene?
Yes. Spodumene, LiAlSi2O6, is a monoclinic pyroxene, hardness 6.5 to 7, the lone Li pyroxene of the 1988 IMA report. Virgilite has its formula but is not one.
Yes. Spodumene, LiAlSi2O6, is a pyroxene: its Handbook sheet says pyroxene group, monoclinic, hardness 6.5 to 7, with two cleavages at about 87 degrees, and the 1988 IMA pyroxene report accepts it as one of 20 pyroxene names, alone in its Li-pyroxene subdivision. The formula alone is not proof: hexagonal virgilite is also LiAlSi2O6.
In short
- Yes, on the sheet and in the nomenclature. The Handbook of Mineralogy spodumene sheet reads Pyroxene group, monoclinic, C2/c. The IMA pyroxene report (Morimoto 1988) formally accepts 20 pyroxene names in six chemical subdivisions; the last, F, Li pyroxene, has one entry: spodumene, LiAlSi2O6. The September 2026 IMA-CNMNC Master List lists it as LiAlSi2O6, status A, 1962 s.p., Sweden.
- The Q-J origin test. Morimoto sorts pyroxenes by Q = Ca + Mg + Fe2+ and J = 2Na per six oxygens. Jadeite, NaAlSi2O6, gives Q 0, J 2; diopside, CaMgSi2O6, Q 2, J 0. Spodumene has no calcium, magnesium, ferrous iron or sodium: Q 0, J 0, the origin of the diagram, which the report says is where spodumene concentrates. Below Q + J = 1.5 a pyroxene goes to the group called Others.
- Worked on a real analysis. Recalculated to six oxygens on standard atomic weights, the sheet’s Pala, California analysis gives Si 1.989, Al 1.013, Li 0.980 and Na 0.013, the sheet’s own (Li0.98Na0.01). Calcium and magnesium are below 0.02 per cent and iron is reported as Fe2O3, so Q is 0 and J is 0.03.
- Documented failure: the formula twin. The IMA list has a second LiAlSi2O6 row: virgilite, approved 1977, from Macusani, Peru. Its Handbook sheet makes it hexagonal, point group 622, with a calculated density of 2.46. The 1988 report says any pyroxene is orthorhombic or monoclinic, so virgilite is not one, and it also gives Q 0, J 0. The Q-J test sorts pyroxenes; it cannot tell you that something is a pyroxene.
- Kunzite and hiddenite are spodumene. Morimoto says hiddenite and kunzite are used for pale emerald-green and lilac gem spodumene, respectively, not accepted as formal pyroxene names but usable as varietal gem names. Its table of 105 discarded pyroxene names sends 7 to spodumene, triphane among them. The lithium figure, 3.73% by mass, and the two-cleavage rule are on the spodumene page.
| Mineral (IMA name) | IMA formula | IMA status, year | Q | J | Q + J | Broad group (1988) | Subdivision (1988 Table 2) | Crystal system (Handbook) |
|---|---|---|---|---|---|---|---|---|
| Spodumene | LiAlSi2O6 | A, 1962 s.p. | 0 | 0 | 0 | Others | F. Li pyroxene (alone) | Monoclinic |
| Jadeite | NaAlSi2O6 | A, 1988 s.p. | 0 | 2 | 2 | Na | E. Na pyroxenes | Monoclinic |
| Aegirine | NaFe3+Si2O6 | A, 1998 s.p. | 0 | 2 | 2 | Na | E. Na pyroxenes | Monoclinic |
| Kosmochlor | NaCr3+Si2O6 | A, 1988 s.p. | 0 | 2 | 2 | Na | E. Na pyroxenes | Monoclinic |
| Diopside | CaMgSi2O6 | A, 1988 s.p. | 2 | 0 | 2 | Quad | C. Ca pyroxenes | Monoclinic |
| Hedenbergite | CaFe2+Si2O6 | A, 1988 s.p. | 2 | 0 | 2 | Quad | C. Ca pyroxenes | Monoclinic |
| Enstatite | Mg2Si2O6 | A, 1988 s.p. | 2 | 0 | 2 | Quad | A. Mg-Fe pyroxenes | Orthorhombic |
| Johannsenite | CaMnSi2O6 | A, 1988 s.p. | 1 | 0 | 1 | Others | C. Ca pyroxenes | Monoclinic |
| Virgilite | LiAlSi2O6 | A, 1977-009 | 0 | 0 | 0 | Not a pyroxene | Not in the report | Hexagonal |
Is spodumene a pyroxene? Yes: the definition in one sentence
A pyroxene is a silicate built of single chains of SiO4 tetrahedra with the formula M2M1T2O6, and spodumene, LiAlSi2O6, is one. That is the definition in Morimoto et al. 1988, Nomenclature of pyroxenes (American Mineralogist 73, 1123): single SiO3 chains of linked tetrahedra, repeating every two tetrahedra, about 0.52 nm, along the c axis, with M2 and M1 octahedral sites and two tetrahedral sites. On the report’s site-allocation procedure, spodumene’s silicon fills the tetrahedral sites, aluminium M1 and lithium M2. The report, approved by the IMA commission’s vote of 20 May 1987, accepts 20 pyroxene names, and its Table 2 lists spodumene as number 20, the only entry under subdivision F, Li pyroxene.
What the sheet says. The Handbook of Mineralogy spodumene sheet gives LiAlSi2O6, Pyroxene group, monoclinic, point group 2/m, space group C2/c; prismatic crystals flattened and striated along {100}, to 12.5 m and 54 t, commonly massive; good {110} cleavage in two directions at about 87°; hardness 6.5 to 7; measured density 3.03 to 3.23, so a 20.00 g piece reads 13.40 to 13.81 g in water. The September 2026 IMA list gives LiAlSi2O6, status A, 1962 s.p., Sweden.
Its pyroxene relatives on this site. Jadeite, NaAlSi2O6, is the sodium pyroxene with the same aluminium and silicon, and its page sets out the cleavage-angle rule that separates pyroxene from amphibole; it is linked, not repeated. Jadeite reads 13.83 to 14.17 g on the same 20.00 g piece. The jade naming question is on is jade a mineral.
Which kind of pyroxene is spodumene? The Q-J origin test
Spodumene sits at the origin of the IMA’s pyroxene diagram, because it has none of the four cations the diagram counts. Morimoto’s method counts cations on six oxygens and plots Q = Ca + Mg + Fe2+ against J = 2Na. The lines Q + J = 2.0 and Q + J = 1.5 bound the common pyroxenes; J/(Q + J) of 0.2 and 0.8 split them into Quad (calcium-magnesium-iron), Ca-Na and Na groups. Below Q + J = 1.5 more than half of the M sites may hold other ions, and the pyroxene belongs to Others.
Worked. On the IMA formulas in the table: jadeite Q 0, J 2, Na group; diopside Q 2, J 0, Quad; spodumene Q 0, J 0. The report says spodumene concentrates at the origin because both Q and J are zero, and that when the procedure was applied to 406 analyses from Deer, Howie and Zussman, most fell between the two Q + J lines, except those of johannsenite and spodumene. Johannsenite, CaMnSi2O6, gives Q 1, because manganese is not counted, and lands in Others too. On the sheet’s Pala analysis, recalculated to six oxygens, Na is 0.013, so J is 0.03 and Q is 0.
What the result means. Spodumene is a pyroxene, but not one of the rock-forming kinds: the report groups donpeacorite, kanoite, johannsenite, petedunnite, esseneite and spodumene as rare in occurrence and unique in chemistry, and treats them together as other pyroxenes. Substitute your own analysis: divide each oxide by its molar mass, scale to six oxygens, and read Q and J.
When the formula misleads: virgilite and the pattern count
Documented failure: LiAlSi2O6 is on the IMA list twice, and only one of the two is a pyroxene. The September 2026 list carries virgilite, LiAlSi2O6, approved as 1977-009, Peru. Its Handbook of Mineralogy virgilite sheet gives the formula LixAlxSi3-xO6, hexagonal, point group 622, crystals to 50 µm in volcanic glass from near Macusani, Puno, with a calculated density of 2.46. The 1988 report says any pyroxene belongs to either the orthorhombic or the monoclinic crystal system. A hexagonal mineral is not a pyroxene, whatever its formula. A plain text search for LiAlSi2O6 finds a third row too, bikitaite, LiAlSi2O6·H2O, status A, 1997 s.p., Zimbabwe: the same atoms plus water, and a different formula.
The Q-J test cannot catch it. Virgilite also gives Q 0, J 0, the same point as spodumene. The diagram sorts minerals already known to be pyroxenes; the structure, which the Handbook records as pyroxene group for spodumene and not for virgilite, is what decides membership. Weight would separate them: 13.40 to 13.81 g in water for a 20.00 g spodumene against 11.87 g at virgilite’s calculated density, though no collector will hold a 20 g virgilite.
The pattern count is not a pyroxene count. A script over the list finds 34 rows whose formula has the pyroxene shape, ending in Si2O6 or an equivalent T2O6 group with no water. Virgilite is one of them, so that 34 is a ceiling on a formula pattern, not a tally of pyroxenes; this page does not classify the others. Of the 20 names the 1988 report accepted, all 20 still have rows, by script, and 13 carry the 1988 special-procedure stamp.
Kunzite, hiddenite and the lithium silicates that are not pyroxenes
Kunzite and hiddenite are spodumene, so they are pyroxenes too. The 1988 report says the names hiddenite and kunzite are often used for (pale) emerald-green and lilac-coloured spodumene of gem quality, respectively, are not accepted as formal pyroxene names, and can be used as varietal gem names. The GIA kunzite facts page calls kunzite the best-known variety of spodumene, with green hiddenite and yellow triphane the others, and gives LiAlSi2O6, hardness 6.5 to 7.0, specific gravity 3.18. The report’s Table 6 of 105 discarded names, parsed by script from the Mineralogical Magazine printing of the same report (52, 535), sends 7 to spodumene: hiddenite, kunzite and triphane to spodumene, soda-spodumene to sodian spodumene, and three to altered spodumene, among them cymatolite and killinite.
Where the sources differ. The GIA kunzite description says kunzite has two perfect cleavage directions; the Handbook sheet says good on {110}. Both describe the same two directions at about 87°; this page prints both. GIA also states that treated and natural colour in kunzite can fade with heat and bright light; the wider question is on which minerals fade in light.
The lithium neighbours that are not pyroxenes. The spodumene sheet lists petalite and eucryptite among its associates. Petalite, LiAlSi4O10, and eucryptite, LiAl(SiO4), have IMA rows but not the M2M1T2O6 formula, and neither Handbook sheet names a pyroxene group; petalite reads 11.71 to 11.74 g on a 20.00 g piece. Pyroxenoids such as wollastonite and rhodonite have single chains too, but the report says their chains repeat every three or more tetrahedra. The classification questions are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.