Khondalite Identification Guide
Identify Khondalite, a high-grade garnet-sillimanite-graphite metamorphic gneiss, by its banding and mineral suite.
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What Khondalite Looks Like
Khondalite is a high-grade (granulite-facies) metamorphic rock—a garnet-sillimanite (and often graphite) gneiss formed from metamorphosed aluminous (pelitic) sediments. In hand sample it is typically gray, pinkish-gray, to rusty brown, often coarse-grained and gneissic (banded/foliated). The signature assemblage is red garnet + needle-like sillimanite + quartz + feldspar, commonly with flakes of graphite giving a dark, sometimes silvery cast. Spinel and rarely corundum may appear.
Quick visual cues
- Coarse, banded/foliated gneiss
- Red garnet porphyroblasts (and rosy color overall)
- Fibrous to needle-like white-gray sillimanite
- Dark gray graphite flakes that mark paper and feel slick
Step-by-Step Field ID Checklist
- Confirm metamorphic texture. Gneissic banding or foliation with segregated light/dark layers.
- Find garnet. Rounded red almandine-rich garnets are nearly always present.
- Spot sillimanite. Fibrous/needle aggregates (fibrolite) or prismatic crystals—a high-temperature index mineral.
- Check for graphite. Soft, gray, greasy flakes that leave a mark = the "graphite" in graphite-khondalite.
- Test component hardness. Garnet 7+, sillimanite ~6.5-7.5, quartz 7, graphite ~1-2 (very soft, contrasting).
- Note the setting. High-grade granulite terranes (e.g., Eastern Ghats, India).
Key Diagnostic Tests
- Rock ID by mineral assemblage: garnet + sillimanite + quartz + K-feldspar (with or without graphite).
- Graphite check: marks paper, greasy feel, gray-black streak, very soft.
- Garnet: isometric, no cleavage, hard, often red.
- Acid: no fizz (silicate rock).
- Density: ~2.7-3.0 g/cm^3 depending on garnet content.
Common Look-Alikes and How to Tell Them Apart
- Garnet-mica schist: lower grade, contains abundant mica (muscovite/biotite) and lacks the high-temperature sillimanite + K-feldspar + graphite suite of true khondalite.
- Kinzigite: a related garnet-cordierite gneiss; khondalite is specifically the sillimanite-graphite (cordierite-poor) type.
- Charnockite: an orthopyroxene-bearing granulite (often greasy green quartz); khondalite is the metasedimentary, garnet-sillimanite member of the same granulite suite.
- Ordinary gneiss: lacks the diagnostic garnet + sillimanite + graphite combination.
Where It Is Found
Khondalite is named after the Khonds (Kondhs) of the Eastern Ghats, India, where it is widespread; it also occurs in granulite belts of Sri Lanka, Antarctica, and other high-grade Precambrian terranes. It is used as a building/dimension stone and is important in studies of deep-crustal metamorphism.
Frequently asked questions
How do you identify Khondalite?
Look for a coarse, banded granulite-facies gneiss containing red garnet, fibrous sillimanite, quartz, and feldspar, very often with soft gray graphite flakes; this garnet-sillimanite-graphite assemblage is diagnostic.
What is Khondalite made of?
It is a metamorphosed aluminous sediment composed mainly of garnet, sillimanite, quartz, and alkali feldspar, commonly with graphite and sometimes spinel, formed under high-temperature granulite-facies conditions.
Khondalite vs charnockite—what's the difference?
Both belong to the granulite suite, but khondalite is the metasedimentary garnet-sillimanite (often graphite-bearing) rock, while charnockite is an orthopyroxene-bearing, often greenish granitoid granulite.
Where is Khondalite found?
It is widespread in the Eastern Ghats of India (its namesake region) and in high-grade Precambrian terranes such as Sri Lanka and Antarctica.
Khondalite identified by the community
Recent Khondalite specimens identified with Rock Identifier.
