Forever SnS Crystal Passport

Madagascan Feldspar

Pronounced: MAD-uh-GAS-kan FELD-spar

Madagascan Feldspar is a commercial name used for feldspar-rich material from Madagascar, often sourced from the island’s extensive granitic pegmatites. Depending on the specimen, the feldspar may belong to the potassium-feldspar or plagioclase groups, so exact mineral identification may require laboratory testing.

Formula: Variable — Feldspar Group * Microcline / Orthoclase: KAlSi₃O₈ * Albite: NaAlSi₃O₈ * Anorthite: CaAl₂Si₂O₈Mohs hardness: Approximately 6–6.5System: Variable depending on the feldspar species

Meet the crystal

About Madagascan Feldspar

Madagascan Feldspar is not one single formally defined mineral species. Instead, it is a commercial name applied to feldspar-rich material originating from Madagascar. The feldspar group is one of the most important families of rock-forming minerals on Earth and includes both alkali feldspars, such as microcline and orthoclase, and the plagioclase series, ranging from albite toward calcium-rich members. Madagascar is particularly famous for its granitic pegmatites, which can contain spectacular feldspar crystals alongside Quartz, Tourmaline, Beryl, Spodumene, Mica and other minerals. Documented Madagascan pegmatites contain Microcline, Albite, Orthoclase and broader Feldspar Group material. Commercial Madagascan Feldspar may therefore vary considerably in appearance. Material may be cream, grey, peach, pink, brown, white or darker in colour and can sometimes display internal flashes or sheen depending on the particular feldspar composition and internal structure. Unless the exact species has been confirmed by mineralogical analysis, the most scientifically responsible description is simply Feldspar Group material from Madagascar.

Explore this passport

Scientific passport

The mineral facts

Observable and measurable properties used to describe and identify this mineral.

Chemical formula: Variable — Feldspar Group * Microcline / Orthoclase: KAlSi₃O₈ * Albite: NaAlSi₃O₈ * Anorthite: CaAl₂Si₂O₈
Mineral class: Silicate — Tectosilicate — Feldspar Group
Crystal system: Variable depending on the feldspar species
Mohs hardness: Approximately 6–6.5
Lustre: Vitreous to pearly
Streak: White
Specific gravity: Typically approximately 2.55–2.76, depending on feldspar composition
Transparency: Transparent to translucent in some individual crystals; commonly translucent to opaque

Common colours

White, cream, grey, pink, peach, tan, brown, pale yellow and occasionally darker grey or blackish tones

Cleavage and fracture

Feldspars characteristically show two good cleavage directions that meet at or close to right angles. Fracture outside cleavage surfaces may be uneven.

From the Earth

How it forms

The geological processes that create this crystal over time.

Formation

Its geological story

Much of Madagascar’s collectible feldspar forms within granitic pegmatites. Pegmatites develop from the final, volatile-rich stages of granitic magma crystallisation. These residual melts can contain abundant water and unusual concentrations of elements, allowing exceptionally large crystals to grow. As the magma cools, feldspar crystallises alongside minerals such as Quartz, Mica, Tourmaline, Beryl and Spodumene. Madagascar contains numerous documented pegmatite districts. For example, the Ampatsikahitra pegmatites in the Sahatany Valley contain both Microcline and Albite alongside Quartz, Tourmaline and Spodumene.

A closer look

Scientific notes

“Madagascan Feldspar” should be treated as a geographic commercial description, not a mineral species. Madagascar contains several documented Feldspar Group minerals. Microcline occurs at localities such as the Anjahamiary pegmatite in Anosy, where the formula is KAlSi₃O₈. Orthoclase has also been scientifically studied from Madagascar, including material from Itrongay. Madagascan pegmatites can additionally contain Albite and potassium feldspars together in the same deposit. This means two specimens sold commercially as “Madagascan Feldspar” may not necessarily be the exact same feldspar species.

Crystal Detective

Look closely. Ask better questions.

Safe observations at home are separated from professional laboratory identification. No single home test can prove every specimen's identity or origin.

Safe checks at home

Look for the typical feldspar appearance: a relatively hard stone with a glassy to pearly lustre and often blocky-looking internal or external structures. Broken or rough material may show flat cleavage surfaces. Feldspar commonly displays two cleavage directions that meet at approximately right angles. Under a strong directional light, some specimens may show flashes or sheen caused by internal structures within the feldspar. Examine the stone with a magnifying glass. Natural specimens may contain variations in colour, internal veils, mineral inclusions or intergrown material from the original pegmatite. Colour alone cannot reliably identify the feldspar species. Do not scratch-test polished retail pieces because several feldspars have very similar hardness and a scratch test will rarely resolve the exact species.

Professional methods

X-ray diffraction is one of the most useful methods for identifying the exact feldspar species. Raman spectroscopy can distinguish many feldspar minerals based on their crystal structures. Petrographic microscopy can identify twinning and other structural features characteristic of particular feldspars. Electron microprobe or SEM-EDS analysis can determine potassium, sodium, calcium, aluminium and silicon concentrations and help classify the material. Detailed compositional analysis is particularly useful for distinguishing potassium feldspar from members of the plagioclase series.

Imitations and treatments

Madagascan Feldspar may be confused with Moonstone, Labradorite, Larvikite, pale Quartz or other feldspar-rich rocks. Some commercial sellers apply attractive names to feldspar based largely on colour or optical effect rather than mineral species. For example, terms such as “Black Moonstone”, “Peach Moonstone” or other Moonstone trade names may represent particular feldspars displaying adularescence, but not every Madagascan Feldspar specimen should automatically be labelled Moonstone. Dyed material is possible, although feldspar is more commonly polished rather than deliberately treated. Resin may occasionally be used to stabilise fractures in carved or polished commercial material. When provenance is known but exact species is not, Madagascan Feldspar is actually a more transparent label than pretending a laboratory identification has been made.

Follow the evidence

Sources and further reading

We show the references used while researching this passport so visitors can check important claims and continue learning.

1
Overview
Sahatany Pegmatite Field (Mt Ibity area), Madagascar
Mindat.org contributors · Mindat.org / Hudson Institute of Mineralogy · Continuously updated database
Primary locality reference demonstrating the diversity of feldspar minerals documented in Madagascar’s Sahatany pegmatites, including Microcline, Orthoclase, Albite and Amazonite alongside Quartz, Mica, Tourmaline and Spodumene.
Checked 25 Sept 2026
2
Science
Les pegmatites de la Sahatany
W. Rakotoarison · Service Géologique de Madagascar · 1964
Historical geological reference documenting the Sahatany pegmatite field and occurrences of Feldspar Group minerals, Microcline and related pegmatite minerals. Useful for establishing that Madagascar’s feldspar deposits are part of complex, well-studied pegmatite systems.
Checked 25 Sept 2026
3
Localities
Ampatsikahitra Pegmatites, Sahatany Valley, Madagascar
Mindat.org contributors · Mindat.org / Hudson Institute of Mineralogy · Continuously updated database
Documents Feldspar Group material, Microcline and Amazonite at Ampatsikahitra alongside Quartz, Tourmaline, Spodumene and Muscovite. Used to support the Vakinankaratra locality entry.
Checked 25 Sept 2026
4
Localities
Marirana Pegmatites, Sahatany Valley, Madagascar
Mindat.org contributors; references include Nadine Ranorosoa and Knut Edvard Larsen · Mindat.org / Hudson Institute of Mineralogy · Continuously updated database
Documents potassium feldspar and Microcline from the Marirana pegmatites and supports their inclusion among important feldspar-bearing localities within the Sahatany field.
Checked 25 Sept 2026
5
Localities
Anjahamiary Pegmatite, Tranomaro, Madagascar
Mindat.org contributors · Mindat.org / Hudson Institute of Mineralogy · Continuously updated database
Documents both Microcline and Albite at the Anjahamiary pegmatite together with Amazonite, Quartz, Beryl, Tourmaline and other pegmatite minerals. Used to demonstrate multiple feldspar species occurring within one Madagascan deposit.
Checked 25 Sept 2026
6
Home identification
Feldspar Group from Itrongay, Madagascar
Mindat.org contributors; referencing Federico Pezzotta · Mindat.org / Hudson Institute of Mineralogy · Continuously updated database
Documents pink to reddish perthitic potassium feldspar and occasional graphic intergrowths with white or smoky Quartz from the Itrongay area. Useful for illustrating the range of appearances possible within commercial Madagascan Feldspar.
Checked 25 Sept 2026
7
Laboratory identification
Itrongay (Itrongahy), Mahasoa Est, Betroka District, Madagascar
Mindat.org contributors; citing Simmons, Falster, Ackermann and earlier mineralogical studies · Mindat.org / Hudson Institute of Mineralogy · Continuously updated database
Particularly important for explaining why laboratory identification matters. Yellow feldspar historically described as Orthoclase from the Itrongay area was subsequently examined by X-ray methods and identified as Sanidine. This provides a real-world example of why appearance or old labels alone cannot always establish exact feldspar species.
Checked 25 Sept 2026
8
Fakes and treatments
Identity of Orthoclase from Itrongay, Madagascar
Knut Edvard Larsen and Mindat.org mineralogical contributors · Mindat.org · 2009 discussion summarising ea
Used not because Itrongay feldspar is fake, but because it demonstrates a major identification issue: material historically sold and labelled as Orthoclase was later shown through X-ray study to be Sanidine. This supports the Passport’s policy of avoiding overly precise species claims without analytical confirmation.
Checked 25 Sept 2026
9
Myths and folklore
Forever SnS Mythical Library — Original Madagascan Feldspar Folklore
Forever SnS · Former SnS Ltd · 2026
The Stone That Could Not Choose a Name and The Island That Collected Colours are original contemporary Forever SnS folklore. They are inspired by Madagascar’s genuine diversity of feldspar minerals and pegmatite deposits but are not presented as traditional Malagasy legends, ancient folklore or documented cultural stories.
Checked 25 Sept 2026
10
Beliefs and traditions
Forever SnS — Modern Feldspar Symbolism Context
Forever SnS · Forever SnS Ltd · 2026
Used to document that Madagascan Feldspar does not have one established ancient spiritual tradition under this commercial name. Any associations with grounding, creativity, intuition or change are treated as contemporary crystal symbolism rather than historical fact or scientifically established effects.
Checked 25 Sept 2026

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