Spherulitic
Texture consisting of roughly spherical or radiating aggregates of fine, commonly fibrous crystals, particularly in silicic volcanic glass or its devitrified products.
Language and route: English scientific derivative of spherule from Greek via Latin/French. English scientific derivative of spherule from Greek via Latin/French
Literal gloss: little-sphere-like radial growth
The name and its history
No securely established individual first coiner · First geological printed use not established
- What does the word literally mean?
- Immediate route: English scientific derivative of spherule from Greek via Latin/French. Linguistic gloss: ‘little-sphere-like radial growth’. This gloss describes language, not a demonstrated early geological theory.
- What did the original author mean?
- Rock microscopists named radial rounded structures to distinguish crystalline intergrowths from homogeneous volcanic glass and from gas cavities.
- Why was the name needed?
- A rounded patch in a lava could be glass, a bubble or a radiating crystal aggregate; these needed separate terms to explain the texture.
- What evidence supported the original concept?
- Radiating fibres and characteristic extinction patterns under crossed polars, together with their growth setting in rhyolite and volcanic glass.
- How has geology changed the concept?
- They may form during primary undercooling or later devitrification; a spherulite does not by itself date the solidification event.
Further historical context
Rock microscopists named radial rounded structures to distinguish crystalline intergrowths from homogeneous volcanic glass and from gas cavities.
A rounded patch in a lava could be glass, a bubble or a radiating crystal aggregate; these needed separate terms to explain the texture.
Radiating fibres and characteristic extinction patterns under crossed polars, together with their growth setting in rhyolite and volcanic glass.
They may form during primary undercooling or later devitrification; a spherulite does not by itself date the solidification event.
Editorial qualification
The first naming act and earliest printed use have not been verified; this is an editorial reconstruction of historical need.
Related names
Variolitic · Obsidian · Rhyolite · Perlite
Sources
- Geological Survey of India, Rock Texture Atlas — Photomicrographs and modern texture definitions
- International Ocean Discovery Program, Expedition 350 methods — Description criteria for volcanic texture and vesicle proportions