How to identify Unakite

To correctly identify Unakite (Unakite (a type of altered granite composed of epidote, pink orthoclase feldspar, and quartz)), 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

   Distinctive mottled or speckled pattern of pistache green (epidote), salmon pink (orthoclase feldspar), and colorless to greyish-white (quartz).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to sub-vitreous for quartz and feldspar, resinous to vitreous for epidote.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granitic to granoblastic, medium to coarse-grained, interlocking crystalline texture.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Individual mineral components (epidote, orthoclase, quartz) may show anhedral to subhedral forms within the rock matrix.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Orthoclase exhibits two distinct cleavages at nearly 90 degrees. Epidote has one perfect cleavage. Quartz has no cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in areas where granitic rocks have undergone regional or contact metamorphism and hydrothermal alteration, particularly in orogenic belts.

Key Facts

Hardness

6-7 (Mohs scale, due to constituent minerals)

Specific Gravity

2.85 - 3.20 (variable, depending on mineral proportions, epidote is denser)

Crystal System

Monoclinic (epidote, orthoclase), Trigonal (quartz) - as a rock, it's an aggregate of these systems.

Color

Green (epidote), pink (orthoclase), colorless/grey (quartz)

Luster

Vitreous to sub-vitreous

Transparency

Opaque to translucent

Fracture

Uneven to conchoidal (quartz), irregular (feldspar, epidote)

Cleavage

Good in orthoclase (two directions at ~90°), perfect in epidote (one direction), absent in quartz.

Composition

An aggregate of epidote (Ca2(Al,Fe)3(SiO4)3(OH)), orthoclase feldspar (KAlSi3O8), and quartz (SiO2).

Physical characteristics

• Crystal Habit: Granular to massive aggregate of anhedral to subhedral crystals.
• Cleavage Type: Good in orthoclase, perfect in epidote, none in quartz.
• Fracture Type: Uneven to conchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous to sub-vitreous.

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