sunstone

sun +‎ stone. Compare Icelandic sólarsteinn.

sunstone (countable and uncountable, plural sunstones)

1. (mineralogy) A translucent form of feldspar having flakes of hematite, used as an ornamental stone.
2. A stone, possibly Icelandic spar, said in late medieval sources to have been used by navigators in the Viking Age and later to find the location of the sun in an overcast sky, possibly via polatization of light.

• heliolite

• aventurine, aventurin, avanturine
• moonstone

• David Barthelmy (1997–2025) “Sunstone”, in Webmineral Mineralogy Database.
• “sunstone”, in Mindat.org‎^[1], Hudson Institute of Mineralogy, 2000–2025.

• neustons