A rare or obsolete mineralogical or geological term; etymology and definition uncertain without additional context.
Possibly a regional or obsolete geological/mineralogical term; etymology unclear—may be a misspelling or variant of an actual mineral name.
Many obscure mineral names come from places or people (alexandrite, scheelite)—if egueiite exists, it probably has that kind of specific origin story, but it's vanished from modern geological databases.
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