felsic

IPA/ˈfel.sɪk/
IPA/ˈfel.sɪk/

felsic — adjective

  • felsicpositive
  • more felsiccomparative
  • most felsicsuperlative

1. describing rock or magma with much silica and many light minerals, especially fe

1.adjectiveC2
Definition

describing rock or magma with much silica and many light minerals, especially feldspar, so it is usually pale in color

Example

Sirin labeled the pale granite sample as felsic during the lab exercise.

pattern: label a sample as felsic

The report calls this lava felsic because it contains much silica.

pattern: call lava felsic

Common collocations
  • felsic rock
  • felsic magma
  • felsic lava
  • felsic mineral
  • felsic crust
Synonyms
  • silica-rich

    a broader descriptive term that explains composition directly, while 'felsic' is the fixed geology label

  • granitic

    often suggests composition or texture similar to granite, so it is narrower than the wider class named by 'felsic'

Antonyms
  • mafic

    the technical opposite for darker rock that contains more iron and magnesium

Grammar Patterns

be felsic

describe [rock or magma] as felsic

felsic + rock / magma / lava / mineral

Usage Note

Mostly used in geology for rock, magma, lava, and minerals. It commonly follows 'be' or appears after verbs such as 'label', 'classify', and 'describe' when scientists identify a sample's composition.

Common Mistakes

The mountain is felsic because it is light gray.
The rock is felsic because it contains much silica and light minerals.
The word describes composition, not color by itself.
This felsic is easy to cut.
This felsic rock is easy to cut.
'felsic' is an adjective, so it needs a noun such as 'rock' or 'magma'.

Synonym discussion

Sense: adjective/1

'Felsic' is a technical geology term, so it is narrower than several everyday-looking alternatives. 'Silica-rich' tells you directly that the rock contains a lot of silica, but it does not automatically suggest the wider group of light minerals that geologists often associate with felsic material. 'Granitic' is closer in appearance and composition, yet it points more specifically to granite-like rock, while 'felsic' can describe magma, lava, minerals, or crust as well. 'Light-colored' only describes what the rock looks like, so it is not a safe substitute: a pale rock is not always felsic. Use 'felsic' when the point is composition, not just color. For example, a lab report may call a magma sample felsic even before anyone comments on how pale it appears.

silica-richgraniticlight-colored

Etymology

English

Coined in English as a blend of 'feldspar' and 'silica'. Geologists created the word to name rock and magma that are rich in those light, silica-bearing materials.