How to identify Fluorescent Calcite and Quartz

To correctly identify Fluorescent Calcite and Quartz (Calcite (CaCO3) and Quartz (SiO2)), 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

   Calcite: Highly variable, often white, colorless, gray, yellow, green, pink, red, brown, black. Quartz: Highly variable, often colorless, white, gray, purple (amethyst), yellow (citrine), pink (rose quartz), brown (smoky quartz). The key identification feature is their fluorescence under UV light, which can be red, orange, pink, blue (calcite) or blue, green, yellow (quartz).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Calcite: Vitreous to sub-vitreous, sometimes pearly on cleavage surfaces. Quartz: Vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Calcite: Can be massive, granular, fibrous, stalactitic, or crystalline. Quartz: Can be massive, granular, cryptocrystalline (e.g., chalcedony), or crystalline.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Calcite: Rhombohedral, scalenohedral, prismatic, tabular. Quartz: Hexagonal prisms with pyramidal terminations, massive, granular.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Calcite: Perfect rhombohedral cleavage in three directions at 74° and 106°. Quartz: None, conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, vugs, and cavities in igneous, metamorphic, and sedimentary rocks. Often found in association with metallic ore deposits, limestone caves, and pegmatites.

Key Facts

Hardness

Calcite: 3 (Mohs); Quartz: 7 (Mohs).

Specific Gravity

Calcite: 2.71 g/cm³; Quartz: 2.65 g/cm³.

Crystal System

Calcite: Trigonal; Quartz: Trigonal (alpha-quartz) or Hexagonal (beta-quartz, high temperature).

Color

Highly variable in visible light; specific fluorescent colors under UV light.

Luster

Vitreous to sub-vitreous (calcite); Vitreous (quartz).

Transparency

Transparent to opaque.

Fracture

Calcite: Conchoidal to uneven; Quartz: Conchoidal.

Cleavage

Calcite: Perfect rhombohedral in 3 directions; Quartz: None.

Composition

Calcite: Calcium Carbonate (CaCO3); Quartz: Silicon Dioxide (SiO2). Fluorescence is due to trace activators.

Physical characteristics

• Crystal Habit: Calcite: Rhombohedral, scalenohedral, prismatic, massive, granular, fibrous. Quartz: Prismatic, massive, granular, cryptocrystalline.
• Cleavage Type: Calcite: Perfect rhombohedral {1011}; Quartz: None.
• Fracture Type: Calcite: Conchoidal to uneven; Quartz: Conchoidal.
• Tenacity: Calcite: Brittle; Quartz: Brittle.
• Luster Type: Calcite: Vitreous to sub-vitreous, sometimes pearly; Quartz: Vitreous.

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