Images
Formula: LiAlSi2O6
Inosilicate (chain silicate), clinopyroxene subgroup,
pyroxene group,
lithium-bearing mineral
Kunzite is a pink gem variety of spodumene
Crystal System: Monoclinic
Specific gravity: 3.1 to 3.2 measured, 3.184 calculated
Hardness: 6½ to 7
Streak: White
Colour: Colourless, white, pink and lilac (kunzite), green (hiddenite), yellow, brown
Solubility: Insoluble in hydrochloric, sulphuric and nitric acid
Common impurities: Fe,Mn,Mg,Ca,Na,K,H2O
Environments:
Spodumene is found almost exclusively as a primary mineral
in lithium-rich
pegmatites.
Localities
The Peatfold pegmatite at Glenbuchat, Strathdon, Aberdeenshire, Scotland, UK, shows a distinctly zoned structure,
broadly symmetrical around a
central core of bright purple mica, probably lepidolite.
The spodumene lens contains striated, fractured intergrown crystals of spodumene, associated with plentiful
tourmaline. This occurrence of spodumene is thought to be the first substantiated
report of the mineral from Scotland.
(JRS 20.30-33).
At the White Picacho District, Arizona, USA, the alteration sequence for spodumene is
spodumene → eucryptite +
albite → muscovite +
albite → muscovite
(AM 67: 97-113).
The zoning sequence within the pegmatite goes from
spodumene + quartz to spodumene +
montebrasite + quartz to
montebrasite + quartz
(R&M 92.2.151)
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, spodumene crystals to 50 cm are associated with
amblygonite-montebrasite,
pollucite and alkali-rich beryl. The Emmons
pegmatite is an example of a highly evolved
boron-lithium-cesium-tantalum
enriched pegmatite
(R&M 94.6.515). Talc pseudomorphs
after spodumene have been found here
(KL p235).
At Plumbago Mountain, Newry, Oxford County, Maine, USA, excavations and core-drilling have exposed a new
albite-quartz-spodumene
pegmatite, the Plumbago North pegmatite. It is
spodumene-rich with more than 50 percent spodumene in some of the upper portions of the
pegmatite. The exposed portion of the
pegmatite is composed principally of
quartz, albite,
muscovite and spodumene.
Microcline is sparse and occurs in the spodumene zone and rare
miarolitic cavities. Montebrasite,
beryl, cassiterite,
almandine-spessartine series
garnets, fluorapatite and
columbite-group species are also present.
Schorl, lepidolite and
pollucite are rare. Columbite-group
minerals include columbite-(Fe),
columbite-(Mn) and
tapiolite-(Fe). Triphylite
pods to 50 cm across with associated iron-dominant secondary
phosphate species are scattered across the spodumene-rich zone. Spodumene and
montebrasite occur in gigantic crystals. One spodumene crystal
exceeded 11 meters in length, and crystals in excess of 2 meters in length are common.
Montebrasite also occurs in very large single crystal masses, with some
exceeding 1.5 meters across
(R&M 97.3.276).
Alteration
petalite to spodumene and quartz
LiAlSi4O10 ⇌ LiAlSi2O6 + 2SiO2
(DHZ 4 p274)
spodumene, quartz and Na+ to
albite
and Li+
LiAlSi2O6 + SiO2 + Na+ → NaAlSi3O8 +
Li+
Whether spodumene breaks down into albite or into
eucryptite and albite depends largely
on the presence or absence of quartz
(AM 67: 97-113).
spodumene and Na+ to eucryptite,
albite
and Li+
2LiAlSi2O6 + Na+ → LiAlSiO4 + NaAlSi3O8
+ Li+
Whether spodumene breaks down into albite or into albite or into
eucryptite and albite depends largely
on the presence or absence of quartz
(AM 67: 97-113).
spodumene, K+ and H+ to muscovite,
quartz and Li+
3LiAlSi2O6 + K+ + 2H+ →
KAl3Si3O10(OH)2 + 3SiO2 + 3Li+
The direct conversion of spodumene to muscovite liberates silica,
but quartz is not usually present in pseudomorphs
of muscovite after spodumene, and this requires an explanation
(AM 67: 97-113).
Back to Minerals