Delaware State Mineral: Sillimanite

Delaware's state mineral is sillimanite, adopted in 1977. Delaware's state fossil is the belemnite, adopted in 1996.

Symbol names and dates are taken from primary state sources linked below. Informal or proposed symbols are not listed unless adopted.

Sillimanite specimen — Sillimanite (not necessarily from Delaware). Photo: Robert M. Lavinsky, CC BY-SA 3.0, via Wikimedia Commons

State mineral: Sillimanite

Adopted:: 1977

Sillimanite is a mineral (Al₂SiO₅) with a Mohs hardness of 6.5–7.5 and a vitreous to silky luster, usually white, gray or brown.

How to identify sillimanite →

Often confused with: Andalusite, Kyanite

State fossil: Belemnite

Adopted:: 1996

Delaware state symbols FAQ

What is the state mineral of Delaware?

Delaware's state mineral is sillimanite, adopted in 1977.

What is the state fossil of Delaware?

Delaware's state fossil is the belemnite, adopted in 1996.

Sources

We cite primary sources (statutes, state government pages, federal regulations, and land-manager sites). Third-party listicles are not used as citations.

Facts & Symbols — State of Delaware (accessed 2026-10-24).
Sillimanite established as Delaware State Mineral — Delaware Geological Survey (accessed 2026-10-24).

Last verified 2026-10-24. Corrections welcome: if a statute has changed, tell us and we'll re-verify.

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