Kenyte Identification Guide
Identify Kenyte, a glassy porphyritic phonolite with rhomb-shaped anorthoclase phenocrysts from volcanoes like Mt. Kenya.
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What Kenyte Looks Like
Kenyte is a distinctive porphyritic volcanic rock—a variety of phonolite (or trachyte) named for Mount Kenya. Its hallmark is rhomb-shaped (lozenge) anorthoclase feldspar phenocrysts set in a dark, glassy to fine-grained groundmass. The matrix is typically dark gray to black and glassy, sometimes vesicular, against which the pale, often glassy, anhedral-to-rhombic feldspar crystals stand out. Some kenyte also carries olivine. Overall it looks like a dark glass studded with squarish-to-diamond-shaped feldspar "blebs."
Quick visual cues
- Dark glassy/aphanitic groundmass
- Conspicuous rhomb- or lens-shaped white-to-clear feldspar phenocrysts
- May be vesicular (gas holes) or flow-banded
- Sometimes minor green olivine grains
Step-by-Step Field ID Checklist
- Identify the texture. Look for a porphyritic rock: large feldspars in a fine/glassy dark matrix.
- Examine phenocryst shape. Rhombic (diamond-shaped) anorthoclase is the signature—straight-sided lozenges, not rounded quartz "eyes."
- Confirm the matrix is volcanic. Glassy, aphanitic, possibly vesicular—indicating rapid cooling lava.
- Test hardness. Feldspars ~6; groundmass scratches glass; overall a hard, tough rock.
- Check for absence of quartz. Phonolites are silica-undersaturated; visible quartz argues against kenyte.
- Note the geologic setting. Found on alkaline volcanoes (Mt. Kenya, Kilimanjaro, Ross Island).
Key Diagnostic Tests
- Rock type, not a single mineral: identify by texture and mineralogy rather than streak.
- Phenocryst mineral: anorthoclase (alkali feldspar), Mohs ~6, two cleavage directions.
- Groundmass: glassy/microcrystalline phonolitic; thin slabs can give a clinking ("phonolite" = ring-stone) sound when struck.
- Acid: no fizz (silicate rock).
- Density: ~2.5-2.6 g/cm^3.
Common Look-Alikes and How to Tell Them Apart
- Ordinary phonolite/trachyte: kenyte is specifically the rhomb-porphyritic, often glassy variety; without the lozenge anorthoclase phenocrysts it is just phonolite.
- Larvikite: also rich in rhomb feldspar but is a coarse, fully crystalline plutonic rock with schillerizing feldspar—kenyte is volcanic and glassy.
- Basalt with feldspar phenocrysts: basalt phenocrysts are blocky plagioclase laths and the rock is denser/darker; kenyte's matrix is phonolitic and lighter.
- Obsidian: pure glass with no rhombic phenocrysts.
Where It Is Found
Kenyte is typical of alkaline stratovolcanoes: the type area is Mount Kenya, with occurrences at Kilimanjaro (Tanzania) and famously at Mount Erebus / Ross Island, Antarctica. It forms from silica-undersaturated alkaline lavas.
Frequently asked questions
What is Kenyte and how do you identify it?
Kenyte is a glassy porphyritic phonolite identified by rhomb-shaped (diamond) anorthoclase feldspar phenocrysts set in a dark, glassy-to-fine volcanic groundmass, with no visible quartz, from alkaline volcanoes such as Mt. Kenya.
What does Kenyte look like?
It looks like a dark gray-to-black glassy lava studded with pale, lozenge or diamond-shaped feldspar crystals; it may be vesicular and sometimes contains small green olivine grains.
Kenyte vs larvikite—what's the difference?
Both contain rhomb-shaped feldspar, but kenyte is a glassy volcanic rock formed from lava, while larvikite is a coarse plutonic rock with large schiller-flashing feldspars.
Where is Kenyte found?
It is named for Mount Kenya and also occurs at Kilimanjaro in Tanzania and at Mount Erebus on Ross Island, Antarctica, forming from silica-undersaturated alkaline lavas.
Kenyte identified by the community
Recent Kenyte specimens identified with Rock Identifier.
