How to identify Peach Moonstone

To correctly identify Peach Moonstone (Orthoclase Feldspar (variety Moonstone)), 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

   Soft peach, orange-pink, or creamy orange, often with a translucent to semi-transparent body color. The adularescence can appear as a bluish-white or silvery sheen.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to pearly on cleavage surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically smooth when polished, but can exhibit a slightly uneven surface on rough specimens due to cleavage.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually found as anhedral to subhedral masses, or as tabular to prismatic crystals within a matrix. Often cut into cabochons for jewelry.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect cleavage in two directions at approximately 90 degrees (specifically, {001} perfect and {010} good).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Occurs in granitic and syenitic pegmatites, hydrothermal veins, and some metamorphic rocks. It is often associated with other feldspars, quartz, mica, and amphiboles.

Key Facts

Hardness

6 - 6.5 on the Mohs scale

Specific Gravity

2.56 - 2.59

Crystal System

Monoclinic

Color

Peach, orange-pink, creamy orange, often with a bluish-white or silvery adularescence

Luster

Vitreous to pearly

Transparency

Translucent to semi-transparent

Fracture

Uneven to conchoidal

Cleavage

Perfect in two directions at approximately 90 degrees ({001} perfect, {010} good)

Composition

Potassium aluminum silicate (KAlSi3O8)

Physical characteristics

• Crystal Habit: Typically massive, granular, or as tabular to prismatic crystals. Often found as anhedral grains in rocks.
• Cleavage Type: Perfect in two directions, forming nearly right angles.
• Fracture Type: Uneven to conchoidal, particularly on surfaces not defined by cleavage.
• Tenacity: Brittle
• Luster Type: Vitreous on crystal faces, pearly on cleavage surfaces.

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