Patuxent river stones; photo from The Patuxent River Agate website (all rights reserved; used by permission).
Official State Gem of Maryland
Maryland designated Patuxent river stone as the official state gem in 2004. All State Gems
Found only in Maryland, Patuxent river stones have extraordinary red and yellow hues that reflect Maryland's state flag. Actually agate (a form of quartz), Patuxent river stones have a glowing translucence that make them perfect for cutting, polishing, and setting into jewelry.