Skarn
Skarn is a calc-silicate metamorphic rock formed where hot intrusive fluids alter carbonate rocks. It can be green, brown, white, red, or mixed and may contain garnet, pyroxene, epidote, or ore minerals.
Skarn properties at a glance
| Type | Metamorphic Rocks |
|---|---|
| Chemical formula | Calc-silicate metamorphic rock; composition varies |
| Mohs hardness | 5.5 |
| Luster | dull |
| Streak | Variable by mineral content |
| Cleavage | Variable by mineral grains |
| Fracture | Uneven to granular |
| Specific gravity | 3.1 |
| Transparency | opaque |
| Common colors | Green, Brown, White, Gray, Red, Black |
| Rarity | uncommon |
Geology & background
Forms when hot mineral-rich fluids from igneous intrusions react with carbonate rocks such as limestone or dolostone, producing calc-silicate minerals.
Skarn deposits have been important sources of metals and are key examples of contact metasomatism.
How to identify Skarn
- Look for a mixed calc-silicate rock with green pyroxene, epidote, garnet, or carbonate minerals.
- Skarn often forms near limestone or dolostone intruded by igneous rock.
- It can be colorful and granular rather than evenly layered.
- Do not identify a green rock as skarn unless the calc-silicate or contact-altered look is visible or locality supports it.
Where Skarn is found
Reported from multiple metamorphic terrains worldwide; verify locality against specimen provenance when available.
How much is Skarn worth?
| Entry-level specimen | $2 |
|---|---|
| Typical collector specimen | $20 |
| Premium specimen | $150+ |
Skarn is usually valued for teaching, field context, locality, texture, mineral content, or unusually attractive specimens rather than high gem value.
Common uses
- Field identification
- Ore deposit study
- Collector specimens
- Education
Interesting facts
- Skarns commonly form near igneous intrusions and carbonate rocks.
- They can host important ore minerals including iron, copper, tungsten, or gold deposits.
- Green diopside, red-brown garnet, and epidote are common skarn minerals.
Care & safety
Skarn can vary in toughness, cleavage, and weathering depending on mineral mix and fabric.
Avoid inhaling dust. Do not cut, grind, or polish unknown metamorphic rocks without eye protection and a properly rated respirator.
