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A silicified mastodon tusk is ancient organic material replaced atom by atom by chalcedony over geological time. Look for the ivory-like internal growth rings or cross-hatched Schreger lines that confirm its biological origin. It is prized both for its paleontological significance and for taking a high polish when cut.

Hardness
6.5-7
Mohs
Luster
Waxy to vitreous
Transparency
Opaque

Is this silicified mastodon tusk?

4-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

  • 1
    Test the hardness
    Try to scratch silicified mastodon tusk with a known reference. Silicified Mastodon Tusk sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
  • 2
    Name the organism
    Decide what left the fossil before worrying about the rock. Organism: Mastodon (genus Mammut). Age: Late Miocene to early Holocene.
  • 3
    Read the luster
    Hold the specimen under a strong light. Luster: waxy to vitreous.
  • 4
    Match the color range
    Compare against the expected color range: white, cream, tan, brown, gray.

Often confused with

Silicified Mastodon Tusk vs. its common look-alikes, and how to tell them apart in the field.

A petrified log section lying on desert ground, red and orange against bare dirt
fossil
Petrified Wood
Mohs 6.5-7

How to tell apart: Luster reads waxy to vitreous on Silicified Mastodon Tusk and vitreous to waxy on Petrified Wood.

Compare →
Blue chalcedony, tumble-polished, Fontenelle Reservoir, Wyoming
mineral
Chalcedony
Mohs 6.5-7
Compare →

Often found alongside silicified mastodon tusk

Minerals reported to co-occur with silicified mastodon tusk. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Mohs hardness
6.5-7
Density
2.6-2.7 g/cm³
Colors
WhiteCreamTanBrownGray
Luster
Waxy to vitreous
Transparency
Opaque
Rarity
Rare
Uses
Collector, Lapidary
Host rock
river gravels, Pleistocene alluvial deposits
Organism
Mastodon (genus Mammut)
Age
Late Miocene to early Holocene

Where rockhounds find silicified mastodon tusk

1 mapped spots

Classic worldwide localities

  • Florida
  • South Carolina
  • Alaska
  • Siberia

Field-hunting tip

Where it forms: river gravels, Pleistocene alluvial deposits. If you start seeing quartz, chalcedony, goethite in float, you are in the right ground. In the U.S., the densest reported localities are in Nebraska. Start trip planning there.

Browse 1 U.S. spots for silicified mastodon tusk →

Common questions

How do you identify silicified mastodon tusk?+
Mohs hardness is 6.5-7. Organism: Mastodon (genus Mammut). Luster: waxy to vitreous. Common colors include white, cream, tan, brown.
Where is silicified mastodon tusk found?+
Notable localities include Florida; South Carolina; Alaska; Siberia.
Can I find silicified mastodon tusk in the United States?+
RockHoundR maps 1 silicified mastodon tusk rockhounding spots across 1 U.S. states. The top states are Nebraska.
What rocks look like silicified mastodon tusk?+
Silicified Mastodon Tusk is most often confused with Petrified Wood, Chalcedony. A quick hardness test and a streak check separate the look-alikes faster than color alone.
What minerals are found with silicified mastodon tusk?+
Silicified Mastodon Tusk commonly co-occurs with Quartz, Chalcedony, Goethite, Clay Minerals. Spotting any of these in float or country rock is a useful trip signal.
What kind of rock does silicified mastodon tusk form in?+
Where it forms: river gravels, Pleistocene alluvial deposits. Working float back to the host body is the standard way to chase a fresh occurrence.
What is silicified mastodon tusk used for?+
Silicified Mastodon Tusk is used in collector, lapidary.

Find silicified mastodon tusk on the map

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