2.6" Sphalerite "Flower", Marcasite & Calcite Association - Missouri

This beautiful specimen contains an association of a deep red sphalerite flower, iridescent marcasite crystal druze and multiple calcite crystals. One side of the specimen is covered in marcasite encrusted dolomite crystals. It comes from the Washington County Aggregates Quarry in the Potosi Barite District of Missouri.

About Calcite Crystals

Calcite crystals are a form of calcium carbonate (CaCO₃) known for their diverse shapes, transparency, and vibrant range of colors. They typically form in rhombohedral, scalenohedral, or prismatic shapes, often with well-defined, sharp edges and glossy surfaces. Calcite crystals are often translucent or transparent, sometimes displaying a double refraction effect where objects viewed through the crystal appear doubled. They can appear in various colors—white, clear, yellow, pink, blue, green, and orange—depending on impurities or trace minerals.

A notable characteristic of calcite is its reaction with weak acids like vinegar, which causes it to effervesce, or fizz, as it releases carbon dioxide. This property makes calcite crystals a key tool in geological identification and studies. Calcite forms in many environments, from sedimentary rocks like limestone and marble to hydrothermal veins.

About Sphalerite

Sphalerite is the most important ore of zinc and a striking mineral prized for its brilliant luster and wide range of colors. Composed of zinc sulfide (ZnS), it commonly forms in cubic or tetrahedral crystals and is found in hydrothermal veins, sedimentary deposits, and metamorphic environments around the world.

Although often brown to black, sphalerite can also occur in shades of honey-yellow, red, orange, and even green. Lighter-colored varieties are sometimes transparent to translucent and can display exceptional dispersion—meaning they separate light into spectral colors more intensely than diamond—giving well-cut specimens a fiery, eye-catching sparkle. Darker specimens are typically opaque with a resinous to submetallic luster.

Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate (CaMg(CO3)2).

The mineral dolomite crystallizes in the trigonal-rhombohedral system. It forms white, tan, gray, or pink crystals. Dolomite is a double carbonate, having an alternating structural arrangement of calcium and magnesium ions. It does not rapidly dissolve in dilute hydrochloric acid as calcite does. Crystal twinning is common.

Dolomite was first described by Carl Linnaeus in 1768, and in 1791 it was described as a rock by the French naturalist and geologist Déodat Gratet de Dolomieu. He first recognized the material in buildings of the old city of Rome, and later as samples collected in the mountains known as the Dolomite Alps of northern Italy.

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DETAILS
SPECIES
Sphalerite, Marcasite, Dolomite and Calcite
LOCATION
Washington County Aggregates Quarry, Potosi Barite District, Washington County, Missouri
SIZE
2.6 x 1.9"
CATEGORY
ITEM
#96380