Rocksday

Rapakivi

Rapakivi is an igneous rock with a Mohs hardness of about 6–7 and a granular luster, usually pink, gray or brown.

Granite with egg-shaped alkali feldspar crystals, each wrapped in a rim of plagioclase.

Rapakivi specimen
Photo: Lysippos, CC BY-SA 3.0, via Wikimedia Commons

How to identify rapakivi

  • Round pink or brown feldspar ovoids.
  • A pale rim around many of the ovoids.
  • Coarse, with quartz and dark mica or hornblende.

Often confused with

Where it's found

  • Southern Finland
  • St. Francois Mountains, Missouri
  • Sweden
  • Ukraine

Uses

Building and facing stone.

Rock tumbling

Great for tumbling.

Did you know?

The Finnish name refers to rock that crumbles into sand. Jakob Sederholm described the type from southern Finland in 1891.

Rapakivi FAQ

What is rapakivi?

Rapakivi is an igneous rock with a Mohs hardness of about 6–7 and a granular luster, usually pink, gray or brown. Granite with egg-shaped alkali feldspar crystals, each wrapped in a rim of plagioclase.

How do you identify rapakivi?

Round pink or brown feldspar ovoids. A pale rim around many of the ovoids. Coarse, with quartz and dark mica or hornblende.

How hard is rapakivi?

Rapakivi has a Mohs hardness of about 6–7. Rapakivi scratches glass, and a steel knife can't scratch it.

Where is rapakivi found?

Notable localities include Southern Finland; St. Francois Mountains, Missouri; Sweden; and Ukraine.

What is rapakivi used for?

Building and facing stone.

Can you tumble rapakivi?

Yes — it tumbles well.

What is rapakivi often confused with?

Rapakivi is most often confused with Granite and Orbicular Granite. Ordinary granite feldspars are blocky, not rimmed ovoids. Orbicular granite has many concentric shells, not a single plagioclase rim.

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