Pyralspite Garnet Identification Guide
Identify pyralspite garnets (pyrope-almandine-spessartine) by their equant dodecahedral crystals, lack of cleavage, and hardness.
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What Pyralspite Garnet Looks Like
"Pyralspite" is the garnet solid-solution series uniting pyrope, almandine, and spessartine — the aluminum-bearing garnets, as opposed to the ugrandite (calcium) series. These garnets are isometric, forming well-shaped equant dodecahedral (12-faced) or trapezohedral (24-faced) crystals. Colors span deep red, brownish-red, purple-red, and orange depending on composition. They are transparent to translucent with a vitreous luster.
They commonly appear as isolated crystals embedded in schist, gneiss, and other metamorphic or igneous rocks.
Step-by-Step Field ID Checklist
- Crystal shape: Look for rounded, well-formed 12- or 24-sided equant crystals.
- Hardness test: It scratches glass readily (Mohs ~6.5–7.5).
- Cleavage check: Confirm no cleavage; fracture is conchoidal to uneven.
- Color/heft: Note red-to-orange color and a fairly high density.
- Host rock: Pyralspite garnets favor aluminous metamorphic rocks (mica schist, gneiss) and some igneous rocks/peridotite.
Key Diagnostic Tests
- Mohs hardness: 6.5–7.5.
- Streak: white.
- Cleavage: none — a key separator from many look-alikes.
- Specific gravity: ~3.6–4.3 (varies with composition; spessartine/almandine are heavier).
- No acid reaction (silicate).
Common Look-Alikes and How to Tell Them Apart
- Ugrandite garnets (grossular, andradite): chemically the calcium series — more often green/yellow, with slightly different density and associations (skarns, calc-silicates); pyralspite garnets are reds-to-oranges from Al-rich rocks.
- Ruby/spinel: harder (8–9) and form different habits; garnet's dodecahedral form and hardness ~7 distinguish it.
- Red tourmaline: forms striated triangular prisms, not equant dodecahedra.
- Red glass: shows bubbles, lacks crystal faces, and is softer.
Diagnosis relies on the dodecahedral/trapezohedral habit, no cleavage, hardness ~7, and metamorphic/igneous setting; member identity (pyrope vs almandine vs spessartine) is judged from color, density, and host rock.
Where It Is Found
Pyralspite garnets are widespread in metamorphic rocks (garnet schist, gneiss, granulite), granite pegmatites, and mantle-derived rocks (pyrope in peridotite and kimberlite). They occur worldwide, including the USA, Brazil, India, Africa, and Sri Lanka.
Frequently asked questions
What is a pyralspite garnet?
Pyralspite is the garnet series combining pyrope, almandine, and spessartine — the aluminum-bearing garnets — typically red to orange, as opposed to the calcium-rich ugrandite series.
How do you identify a pyralspite garnet?
Look for equant dodecahedral or trapezohedral crystals, a hardness of about 6.5–7.5, no cleavage, conchoidal fracture, and a red-to-orange color, usually hosted in schist or gneiss.
Pyralspite vs ugrandite garnet — what's the difference?
Pyralspite garnets are the aluminum series (pyrope, almandine, spessartine), usually red-orange in aluminous rocks, while ugrandite garnets are the calcium series (uvarovite, grossular, andradite), often green-yellow in skarns and calc-silicates.
How can you tell garnet from red glass or ruby?
Garnet forms dodecahedral crystals with no cleavage and a hardness around 7; ruby is harder (9) with different crystals, and red glass shows bubbles, lacks crystal faces, and is softer.