How to identify Sugilite

To correctly identify Sugilite (KNa2(Fe,Mn,Al)2Li3Si12O30), 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

   Varies from light pinkish-purple to deep reddish-purple, often with black (manganese oxide) or yellowish-brown (iron oxide) inclusions. The most desirable color is a uniform, intense royal purple.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to resinous, sometimes waxy in massive forms.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, granular, or compact. Rarely found as distinct crystals.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hexagonal system, but well-formed crystals are extremely rare. Usually occurs as anhedral grains or massive aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Poor to indistinct on {0001}, often not observed in massive material.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in alkali-rich, silica-deficient igneous rocks or in metamorphic rocks that have undergone metasomatism, particularly associated with manganese deposits. It is a product of complex geochemical processes.

Key Facts

Hardness

5.5-6.5 on the Mohs scale

Specific Gravity

2.74-2.80 g/cm³

Crystal System

Hexagonal (dihexagonal dipyramidal class)

Color

Purple, pinkish-purple, reddish-purple; can have black or yellowish-brown inclusions

Luster

Vitreous to resinous, sometimes waxy

Transparency

Translucent to opaque

Fracture

Conchoidal to uneven

Cleavage

Poor to indistinct on {0001}

Composition

Potassium sodium iron manganese aluminum lithium silicate

Physical characteristics

• Crystal Habit: Typically massive, granular, or compact aggregates; rarely as small, prismatic hexagonal crystals.
• Cleavage Type: Poor to indistinct, often not observed.
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Vitreous to resinous.

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