How to identify Dolomite with Quartz Geode

To correctly identify Dolomite with Quartz Geode (Dolomite (CaMg(CO3)2) with 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

   Outer shell typically grey, tan, or brownish (dolomite). Inner quartz crystals are usually colorless, white, or translucent, but can be tinted by impurities (e.g., iron oxides for yellow/orange). Dolomite crystals can be white, pink, or yellowish.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Dolomite: Vitreous to pearly. Quartz: Vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Outer surface can be rough or nodular. Inner surface is crystalline, with distinct crystal faces of quartz and often dolomite.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Dolomite typically forms rhombohedral crystals, often with curved faces. Quartz forms hexagonal prisms terminated by hexagonal pyramids.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Dolomite exhibits perfect rhombohedral cleavage in three directions. Quartz has no cleavage, but exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in sedimentary rock formations, particularly limestones and dolomites, where groundwater circulation has allowed for dissolution and subsequent mineral precipitation in cavities. Also found in some shales and evaporite deposits.

Key Facts

Hardness

Dolomite: 3.5-4 on Mohs scale. Quartz: 7 on Mohs scale.

Specific Gravity

Dolomite: 2.85 g/cm³. Quartz: 2.65 g/cm³.

Crystal System

Dolomite: Trigonal. Quartz: Trigonal.

Color

Dolomite: White, grey, pink, green, brown. Quartz: Colorless, white, purple, yellow, brown, black (depending on variety and impurities).

Luster

Dolomite: Vitreous to pearly. Quartz: Vitreous.

Transparency

Dolomite: Translucent to transparent. Quartz: Transparent to translucent.

Fracture

Dolomite: Conchoidal to subconchoidal. Quartz: Conchoidal.

Cleavage

Dolomite: Perfect rhombohedral in three directions. Quartz: None.

Composition

Dolomite: Calcium Magnesium Carbonate (CaMg(CO3)2). Quartz: Silicon Dioxide (SiO2).

Physical characteristics

• Crystal Habit: Dolomite: Rhombohedral, often with curved faces, granular, massive. Quartz: Prismatic, often terminated by pyramids, massive, granular.
• Cleavage Type: Dolomite: Perfect rhombohedral {1011}. Quartz: None.
• Fracture Type: Dolomite: Conchoidal to subconchoidal. Quartz: Conchoidal.
• Tenacity: Dolomite: Brittle. Quartz: Brittle.
• Luster Type: Dolomite: Vitreous to pearly. Quartz: Vitreous.

Explore Dolomite with Quartz Geode