Tonalite

Tonalite is an igneous, plutonic (intrusive) rock, of felsic composition, with phaneritic texture. Feldspar is present as plagioclase (typically oligoclase or andesine) with 10% or less alkali feldspar. Quartz is present as more than 20% of the rock. Amphiboles and pyroxenes are common accessory minerals.

Additional recommended knowledge

How to ensure accurate weighing results every day?

What is the Correct Way to Check Repeatability in Balances?

How to quickly check pipettes?

In older references tonalite is sometimes used as a synonym for quartz diorite, however the current IUGS classification defines tonalite as having greater than 20% quartz and quartz diorite with from 5 to 20% quartz.

Trondhjemite is an orthoclase-deficient variety of tonalite with minor biotite as the only mafic mineral, named after Norway's third largest city, Trondheim.

See also

• Valcamonica