Montana State Gem: Sapphire, Montana agate

Montana's state gem stones are sapphire and Montana agate, adopted in 1969. Montana's state fossil is Maiasaura peeblesorum, adopted in 1985.

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

Sapphire specimen — Sapphire (not necessarily from Montana). Photo: James St. John, CC BY 2.0, via Wikimedia Commons

State gem stone: Sapphire

Adopted:: 1969
Law:: MCA 1-1-505; chapter 20, Laws of 1969

Sapphire is a mineral (Al₂O₃) with a Mohs hardness of 9 and an adamantine to vitreous luster, usually blue, yellow, pink or orange.

How to identify sapphire →

Often confused with: Benitoite, Iolite, Kyanite

Agate specimen — Agate (not necessarily from Montana). Photo: James St. John, CC BY 2.0, via Wikimedia Commons

State gem stone: Montana agate

Adopted:: 1969
Law:: MCA 1-1-505; chapter 20, Laws of 1969
Variety:: Montana agate

It is a variety of agate. Agate is a mineral (SiO₂) with a Mohs hardness of 6.5–7 and a waxy to vitreous luster, usually red, orange, white, gray, brown or blue.

How to identify agate →

Often confused with: Blue Lace Agate, Carnelian, Chalcedony

Also an official symbol of: Kentucky, Louisiana, Maryland, Minnesota, Nebraska, South Dakota, Tennessee

State fossil: Maiasaura peeblesorum

Adopted:: 1985
Law:: MCA 1-1-509; chapter 37, Laws of 1985

The code calls it a duck-billed dinosaur. The 1985 bill says the finds are from the Choteau area and that the species name honors the Peebles family.

Montana state symbols FAQ

What is the state gem stone of Montana?

Montana's state gem stones are sapphire and Montana agate, adopted in 1969 (MCA 1-1-505; chapter 20, Laws of 1969).

What is the state fossil of Montana?

Montana's state fossil is Maiasaura peeblesorum, adopted in 1985 (MCA 1-1-509; chapter 37, Laws of 1985).

Sources

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

Montana Code Annotated § 1-1-505, State gem stones — Montana Legislature (accessed 2026-10-23).
Montana Code Annotated § 1-1-509, State fossil — Montana Legislature (accessed 2026-10-23).
House Bill 81 (1985), designating the state fossil — Montana Legislature (accessed 2026-10-23).

Last verified 2026-10-23. Corrections welcome: if a statute has changed, tell us and we'll re-verify.

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