A form of obsidian characterized by spherlulites formed by cracking of the volcanic glass during cooling, used as insulation or in plant growth media.
- ‘Use a premixed potting soil, usually composed of sand, peat moss, fine bark, perlite or vermiculite.’
- ‘With hot adhesives, however, it has to be paired with an insulation cover board of another type, such as perlite or wood fiber.’
- ‘Most soil-less mixes are a combination of peat, perlite & vermiculite and drain very quickly.’
- ‘The mix we use contains compost, peat, perlite, rock phosphates, blood meal, calcite clay and gypsum.’
- ‘These soil mixtures should include sand, peat moss, perlite, vermiculite, and fir bark for adequate drainage.’
Mid 19th century: from French, from perle ‘pearl’.
We take a look at several popular, though confusing, punctuation marks.