![Dolomite on Prehnite (Saddle-shaped Dolomite) (Dolomite [CaMg(CO3)2] on Prehnite [Ca2Al(AlSi3O10)(OH)2]) — mineral](https://media.rockidentification.com/e87ff3a9-e45f-4f45-8b3f-37184a3b1e56-compressed.jpg)
mineral
Dolomite on Prehnite (Saddle-shaped Dolomite)
Dolomite [CaMg(CO3)2] on Prehnite [Ca2Al(AlSi3O10)(OH)2]
Hardness: 3.5-4 (Dolomite) and 6-6.5 (Prehnite). Color: Pearly white to cream crystals on a pale green/yellow matrix. Luster: Vitreous to pearly. Crystal structure: Trigonal (rhombohedral) for Dolomite, Orthorhombic for Prehnite. Cleavage: Perfect rhombohedral.
- Hardness
- 3
- Color
- Pearly white to cream crystals on a pale green/yellow matrix
- Luster
- Vitreous to pearly
Identified More mineral →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3.5-4 (Dolomite) and 6-6.5 (Prehnite). Color: Pearly white to cream crystals on a pale green/yellow matrix. Luster: Vitreous to pearly. Crystal structure: Trigonal (rhombohedral) for Dolomite, Orthorhombic for Prehnite. Cleavage: Perfect rhombohedral.
Formation & geological history
Formed through hydrothermal processes where magnesium-rich fluids react with limestone or are precipitated in cavities. Often found in basaltic vugs or sedimentary basins. This specific 'saddle' shape is caused by crystal lattice distortion during growth.
Uses & applications
Primarily a collector's mineral specimen. Industrial dolomite is used in cement, as a source of magnesium, and as a flux in steel making. Prehnite is sometimes used as a minor gemstone or ornamental stone.
Geological facts
The characteristic curved 'saddle' shape of the dolomite crystals is a classic feature highly prized by mineralogists. Fine combinations of white dolomite on mint-green prehnite are most famously sourced from the Kayes Region of Mali.
Field identification & locations
Identify in the field by the curved rhombohedral crystals and the reaction to warm dilute hydrochloric acid (effervescence). Common locations include Mali, Morocco, and various trap rock quarries in New Jersey, USA. Collectors look for undamaged crystal 'saddles' and contrasting matrix colors.
More like this
Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Nephrite Jade
Nephrite
Mineral/Rock
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
Metamorphic Rock
![Green Apatite on Albite (Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]) — mineral](https://media.rockidentification.com/2391a63f-fb20-47d5-af9a-2035851eb32e-thumbnail.jpg)
Green Apatite on Albite
Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]
mineral
Epidote
Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)
mineral