Larvikite Identification Guide

What Larvikite Looks Like

Larvikite is a coarse-grained intrusive igneous rock (a monzonite/syenite) dominated by interlocking feldspar crystals that show a striking silvery-blue to gray schiller (a sheen similar to labradorescence). The background is dark gray to bluish-gray to almost black, with large, blocky feldspar grains that flash blue, silver, or sometimes gold as the rock is tilted. It is widely used as a building and countertop stone, sold under names like "Blue Pearl" and "Emerald Pearl" granite (a commercial misnomer - it is not true granite).

Step-by-Step Field ID Checklist

1. Tilt under light - look for blue/silver schiller flashing across large feldspar grains.
2. Note the coarse, interlocking crystal texture - it is a rock, with grains, not a single gem.
3. Check the dark gray-blue base color.
4. Test hardness - feldspar dominates, Mohs ~6-6.5; scratches glass.
5. Look for sparse dark minerals (pyroxene, amphibole, biotite) between the feldspars.

Key Diagnostic Tests

• Schiller (diagnostic): Blue-silver sheen from feldspar exsolution lamellae across large grains.
• Mohs hardness ~6-6.5: Feldspar scratches glass; not scratched easily by a knife.
• Cleavage: Feldspar grains show flat cleavage faces that carry the flash.
• Granular rock texture: Multiple visible mineral grains distinguish it from a single labradorite crystal.
• No acid reaction; not magnetic (minor magnetite possible).

Common Look-Alikes and How to Tell Them Apart

• Labradorite (the mineral): Single mineral with one continuous flash; larvikite is a whole rock packed with feldspar grains each showing schiller.
• True granite: Light-colored with quartz, feldspar, and mica but no blue schiller; larvikite is feldspar-dominated and quartz-poor.
• Gabbro/norite: Dark plutonic rocks but lacking the blue feldspar schiller.
• Anorthosite: Plagioclase-rich and may show some flash, but larvikite's feldspar is alkali-rich ternary feldspar with the characteristic blue-silver sheen.
• Blue Pearl/Emerald Pearl "granite": These are commercial names for larvikite itself.

Where Larvikite Is Found

Larvikite is named for Larvik in the Oslo Rift region of southern Norway, its primary source and the world's main quarrying area. It formed in a Permian-age alkaline intrusion and is exported globally as dimension stone.