mineral

Chalcedony (specifically Agate and Carnelian variety)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Hardness: 6.5-7 on Mohs scale; Color: Yellow, orange, tan, and translucent white; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Hardness: 6
Color: Yellow, orange, tan, and translucent white
Luster: Waxy to vitreous

Identified July 6, 2026More mineral →

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Physical properties

Formation & geological history

Formed via the deposition of silica from groundwater in cavities of volcanic and sedimentary rocks. Usually found as nodules or vein fillings in igneous environments.

Uses & applications

Used primarily in jewelry (cabochons, beads), decorative carvings, and as a collector's gemstone. Historically used for making tools due to its toughness.

Geological facts

Chalcedony was used as early as the Bronze Age in the Mediterranean region for cylinder seals and amulets. It is the parent category for stones like carnelian, onyx, and jasper.

Field identification & locations

Field identification involves checking for a waxy luster, conchoidal (shell-like) fracture, and the ability to scratch glass. These specimens appear to be alluvial or weathered water-worn pebbles.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Gypsum (variety Selenite or Alabaster)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Nephrite Jade

Nephrite

Mineral/Rock

Granite

Granite (Phaneritic intrusive igneous rock)

igneous