Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Apatite is a group of phosphate minerals, typically referring to fluorapatite (Ca5(PO4)3F), chlorapatite (Ca5(PO4)3Cl), and hydroxylapatite (Ca5(PO4)3OH). It is the most common phosphate mineral and is widespread in various rock types. Its name comes from the Greek word 'apatein', meaning 'to deceive', due to its resemblance to other minerals like beryl, tourmaline, and olivine. Apatite is a relatively soft mineral, ranking 5 on the Mohs scale of hardness, making it a key reference mineral for this scale.
How to Identify
- Color
- Highly variable; commonly green, blue, yellow, brown, pink, purple, or colorless. Can also be white, gray, or black.
- Luster
- Vitreous to sub-resinous.
- Texture
- Typically crystalline, often forming hexagonal prisms. Can also be massive, granular, or botryoidal.
- Crystal Form
- Hexagonal system, typically forming prismatic crystals with pyramidal terminations. Can also be tabular or acicular.
- Cleavage
- Poor to indistinct on {0001} and {1010}.
- Geological Environment
- Igneous rocks (granites, pegmatites, carbonatites), metamorphic rocks (marbles, gneisses), sedimentary rocks (phosphorites), hydrothermal veins.
Key Facts
- Hardness: 5 (Mohs scale)
- Specific Gravity: 3.16 - 3.22
- Crystal System: Hexagonal
- Color: Highly variable (green, blue, yellow, brown, pink, purple, colorless, etc.)
- Luster: Vitreous to sub-resinous
- Transparency: Transparent to translucent
- Fracture: Conchoidal to uneven
- Cleavage: Poor to indistinct on {0001} and {1010}
- Composition: Calcium phosphate with fluoride, chloride, or hydroxyl anions
Quick Check
- Color: Variable (green, blue, yellow, brown, pink, purple, colorless, white, gray, black)
- Luster: Vitreous to sub-resinous
- Streak: White
Physical Characteristics
- Crystal Habit: Prismatic, tabular, acicular, massive, granular, botryoidal
- Cleavage Type: Poor to indistinct basal and prismatic
- Fracture Type: Conchoidal to uneven
- Tenacity: Brittle
- Luster Type: Vitreous to sub-resinous
Formation
Apatite forms in a wide variety of geological environments. It is a common accessory mineral in igneous rocks (e.g., granites, syenites, carbonatites, pegmatites), metamorphic rocks (e.g., marbles, gneisses, schists), and sedimentary rocks (e.g., phosphorites, shales, sandstones). It can crystallize directly from magma, form through hydrothermal processes, or precipitate from aqueous solutions in sedimentary basins. Biogenic apatite is the primary mineral component of bones and teeth in vertebrates.
Usage
Apatite is the primary ore mineral for phosphorus, which is essential for fertilizers, phosphoric acid, and various chemical industries. High-quality, transparent apatite crystals are sometimes cut as gemstones, though their relative softness (Mohs 5) limits their durability. Synthetic hydroxylapatite is used in biomedical applications for bone grafts and dental implants due to its biocompatibility.
Age Distribution
Found in rocks of all ages, from Precambrian to Cenozoic.
Where to Find
Russia (Kola Peninsula)
Known for large deposits of apatite, particularly in the Khibiny and Lovozero massifs, associated with alkaline igneous rocks.
Brazil (Minas Gerais)
Produces fine gem-quality apatite crystals, often in vibrant colors, from pegmatites and metamorphic rocks.
Canada (Ontario, Quebec)
Historically significant apatite mining regions, particularly for fluorapatite, found in metamorphic and igneous rocks.
United States (Florida, Idaho, Tennessee)
Major sources of sedimentary phosphorite deposits, which are primarily composed of cryptocrystalline apatite (collophane).
Mexico (Durango)
Known for producing excellent, often large, green and yellow apatite crystals from pegmatites.
Myanmar (Mogok)
Source of gem-quality apatite, often associated with ruby and sapphire deposits.
Finding Tips
Check for Hexagonal Crystals
Apatite often forms distinctive hexagonal prismatic crystals, which can be a good indicator in the field.
Test Hardness
With a Mohs hardness of 5, apatite can be scratched by a steel file (hardness ~6.5) but will scratch glass (hardness ~5.5). This helps distinguish it from harder minerals like quartz or softer ones like calcite.
Look for Associated Minerals
In igneous and metamorphic environments, apatite is often found with feldspar, quartz, mica, hornblende, and calcite. In sedimentary phosphorites, it's typically massive and associated with chert, clay, and organic matter.
Consider Color Variation
Due to its wide range of colors, don't rule out apatite based on color alone. Look for other diagnostic features.
Similar Rocks
Beryl
Be3Al2Si6O18
Also known as: Emerald, Aquamarine
Tourmaline
Na(Mg,Fe,Li,Al)3Al6(BO3)3Si6O18(OH)4
Also known as: Schorl, Elbaite
Olivine
(Mg,Fe)2SiO4
Also known as: Peridot
Diopside
CaMgSi2O6
Also known as: Chrome Diopside
Scientific Classification
- Mineral Class
- Phosphate
- Group
- Apatite Group
- Crystal System
- Hexagonal
- Chemical Formula
- Ca5(PO4)3(F,Cl,OH)
- Composition
- Calcium phosphate with varying amounts of fluoride, chloride, and hydroxyl ions substituting for each other in the anion site.
Explore Apatite
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.