Skip to main content


sillar A local Peruvian name for ignimbrites that have been pervasively altered by vapour-phase crystallization. The alteration of original pumice and glass shards involves deposition of tridymite, cristobalite, and alkali feldspar that occurs as drusy infills of the matrix and pumice cavities in the upper parts of ignimbrite cooling units. The gas is derived by diffusion from juvenile glassy fragments within the flow and from heated groundwater percolating through the flow. The resulting material makes excellent, lightweight, easily worked building stone, usually white. The city of Arequipa, southern Peru, is renowned for its buildings of sillar.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"sillar." A Dictionary of Earth Sciences. . 20 Apr. 2019 <>.

"sillar." A Dictionary of Earth Sciences. . (April 20, 2019).

"sillar." A Dictionary of Earth Sciences. . Retrieved April 20, 2019 from

Learn more about citation styles

Citation styles gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, cannot guarantee each citation it generates. Therefore, it’s best to use citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

The Chicago Manual of Style

American Psychological Association

  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.