RocksdayFusulinid vs Nummulite
To tell Fusulinid from Nummulite: Nummulites are coin-shaped and much younger (Eocene and later).
Wheat- or rice-shaped shells of late Paleozoic foraminifera. A limestone can be made of almost nothing else.
Photo: Wilson44691, CC BY-SA 3.0
Coin-shaped shells of giant foraminifera, common in Eocene and Miocene limestones around the Mediterranean.
Photo: Wilson44691, Public domain
Key differences
- Nummulites are coin-shaped and much younger (Eocene and later).
- Fusulinids are rice-grain shaped and are older, from the late Paleozoic.
Side by side
| Property | Fusulinid | Nummulite |
|---|---|---|
| Type | Fossil | Fossil |
| Mohs hardness | 3–4 | 3 |
| Luster | Dull | Dull |
| Colors | Gray, White, Brown | White, Gray, Yellow |
| Crystal system / structure | Rice-grain foraminifera in limestone | Coin-shaped foraminifera |
| Specific gravity | 2.6–2.7 | 2.6–2.7 |
| Found in | Kansas; Texas | Egypt; Mediterranean region |
Properties that are the same for both are grayed out.
How to identify fusulinid
- Tiny grains the size of rice or wheat in limestone.
- A broken grain shows coiled chambers.
- The rock fizzes in acid.
Structure: Rice-grain foraminifera in limestone
Full Fusulinid guide →How to identify nummulite
- Flat disks from about a centimeter to a few centimeters across.
- A broken one shows a tight spiral of tiny chambers.
- The limestone fizzes in acid.
Structure: Coin-shaped foraminifera
Full Nummulite guide →More comparisons
Frequently asked questions
What is the difference between fusulinid and nummulite?
Fusulinid is a fossil with a Mohs hardness of about 3–4 and a dull luster, usually gray, white or brown. Nummulite is a fossil with a Mohs hardness of about 3 and a dull luster, usually white, gray or yellow.
How can you tell fusulinid from nummulite?
Nummulites are coin-shaped and much younger (Eocene and later). Fusulinids are rice-grain shaped and are older, from the late Paleozoic.
Could you tell them apart from a blurry close-up?
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