How to identify Aquamarine in matrix

To correctly identify Aquamarine in matrix (Beryl variety Aquamarine (Be3Al2Si6O18)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Pale blue to deep blue, sometimes with a greenish tint. The color is typically uniform within a single crystal, though zoning can occur. The matrix color will vary depending on the host rock (e.g., white/pink for feldspar, grey for quartz, silvery for muscovite).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) on crystal faces and fracture surfaces for aquamarine. The matrix minerals will have their characteristic lusters (e.g., vitreous for quartz, pearly for muscovite, dull to vitreous for feldspar).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Aquamarine crystals are typically smooth on their prismatic faces, sometimes with fine striations. The matrix can be granular (pegmatite), massive, or foliated (schist), depending on the rock type.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Aquamarine forms hexagonal prisms, often terminated by pinacoids or pyramidal faces. Crystals can be euhedral (well-formed) to anhedral (irregularly shaped) depending on growth conditions. When in matrix, well-formed crystals are highly sought after.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Aquamarine has imperfect basal cleavage {0001}, which is rarely observed. The matrix minerals will have their own distinct cleavage patterns (e.g., perfect cleavage in feldspar and muscovite, no cleavage in quartz).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Primarily granitic pegmatites, but also hydrothermal veins and sometimes metamorphic rocks. Look for coarse-grained igneous rocks or veins cutting through other rock types.

Key Facts

Hardness

7.5 - 8 on the Mohs scale (for aquamarine)

Specific Gravity

2.68 - 2.80 g/cm³ (for aquamarine)

Crystal System

Hexagonal

Color

Blue, blue-green

Luster

Vitreous

Transparency

Transparent to translucent

Fracture

Conchoidal to uneven

Cleavage

Imperfect basal {0001}

Composition

Beryllium aluminum silicate (Be3Al2Si6O18)

Physical characteristics

• Crystal Habit: Prismatic, typically hexagonal prisms, often striated parallel to the c-axis. Can be massive or granular.
• Cleavage Type: Imperfect basal {0001}, rarely observed.
• Fracture Type: Conchoidal to uneven, brittle.
• Tenacity: Brittle
• Luster Type: Vitreous (glassy)

Explore Aquamarine in matrix