Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Ocean Jasper is a unique and highly sought-after variety of orbicular jasper, characterized by its distinctive spherical or 'orb' patterns. These orbs can vary greatly in size, color, and arrangement, often appearing as concentric rings, eyes, or swirling patterns. The base colors range widely, including greens, yellows, reds, browns, creams, whites, and occasionally pinks or blues. It is a form of chalcedony, which is a cryptocrystalline variety of quartz, meaning its crystals are too fine to be seen without high magnification. Its formation is intimately linked to ancient volcanic activity along coastlines, giving it its 'oceanic' name.
How to Identify
- Color
- Extremely variable, including shades of green, yellow, brown, red, cream, white, pink, and occasionally blue. Often multi-colored within a single specimen.
- Luster
- Vitreous to waxy, dull on unpolished surfaces.
- Texture
- Typically smooth and fine-grained when polished. Unpolished surfaces can be slightly rough or granular.
- Crystal Form
- Cryptocrystalline, meaning individual crystals are microscopic and not visible to the naked eye. Forms botryoidal, mammillary, or nodular masses with characteristic orbicular patterns.
- Cleavage
- None, due to its cryptocrystalline nature.
- Geological Environment
- Hydrothermal veins and infillings within rhyolitic volcanic rocks, particularly those formed in coastal or submarine environments. Often found as nodules or seams within altered volcanic tuffs and flows.
Key Facts
- Hardness: 6.5-7 on the Mohs scale
- Specific Gravity: 2.58-2.64
- Crystal System: Trigonal (cryptocrystalline aggregates)
- Color: Highly variable; green, yellow, red, brown, cream, white, pink, blue, often multi-colored with orbicular patterns.
- Luster: Vitreous to waxy, dull on unpolished surfaces.
- Transparency: Opaque to translucent.
- Fracture: Conchoidal to uneven.
- Cleavage: None.
- Composition: Silicon dioxide (SiO2) with various mineral inclusions.
Quick Check
- Color: Multi-colored with distinct orbicular patterns (greens, yellows, reds, creams, whites, browns, pinks).
- Luster: Waxy to vitreous.
- Streak: White.
Physical Characteristics
- Crystal Habit: Cryptocrystalline aggregates forming botryoidal, mammillary, or nodular masses with characteristic orbicular structures.
- Cleavage Type: Absent.
- Fracture Type: Conchoidal to uneven, splintery.
- Tenacity: Brittle.
- Luster Type: Vitreous to waxy.
Formation
Ocean Jasper forms from silica-rich hydrothermal fluids that percolate through volcanic rocks, specifically rhyolite flows and tuffs. The distinctive orbicular patterns are believed to result from the rhythmic precipitation of silica (chalcedony) and other minerals (such as quartz, feldspar, and various oxides) around a central nucleus or from the spherulitic growth of chalcedony within vesicles or vugs. The presence of various trace elements and mineral inclusions contributes to its wide range of colors and patterns. The specific geological environment involves submarine volcanic activity, where silica-rich solutions interact with existing rock formations.
Usage
Primarily used as an ornamental stone, for lapidary purposes (cabochons, spheres, carvings), and in jewelry. It is also popular among mineral collectors and for metaphysical practices.
Age Distribution
Late Cretaceous to Paleocene (approximately 70-50 million years ago)
Where to Find
Marovato, Madagascar
The primary and historically significant source of Ocean Jasper. It is found along the northwestern coast of Madagascar, accessible only during low tide by boat. The deposits are within ancient rhyolitic volcanic flows.
Kabamby, Madagascar
A more recently discovered deposit, also in Madagascar, yielding material with slightly different color palettes and orbicular patterns, often with larger orbs and more vibrant colors.
Finding Tips
Location Specificity
Ocean Jasper is currently known from only two specific locations in Madagascar. Any material marketed as 'Ocean Jasper' from other localities should be viewed with skepticism.
Orbicular Patterns
The defining characteristic is the presence of distinct, often concentric, spherical patterns. Absence of these patterns suggests it may be a different type of jasper or chalcedony.
Hardness Test
As a variety of chalcedony, it should scratch glass (Mohs hardness 6.5-7). This helps distinguish it from softer imitations.
Visual Inspection
Examine for a waxy to vitreous luster on polished surfaces and a wide range of colors and patterns. The patterns are typically well-defined and often appear 'three-dimensional' due to varying mineral inclusions.
Similar Rocks
Orbicular Granite
Orbicular Granitoid
Also known as: Orbicular Diorite, Orbicular Gabbro
Leopard Skin Jasper
Jasper (Leopard Skin variety)
Also known as: Leopard Jasper
Kambaba Jasper
Stromatolite Jasper
Also known as: Crocodile Jasper
Scientific Classification
- Mineral Class
- Silicates (Tectosilicates)
- Group
- Quartz Group (Chalcedony variety)
- Crystal System
- Trigonal (microcrystalline)
- Chemical Formula
- SiO2
- Composition
- Silicon dioxide, often with trace amounts of iron, aluminum, manganese, and other elements contributing to color and pattern.
Explore Ocean Jasper
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.