Broken Arrow Rock Shop

08/08/2026

This colorful specimen is a piece of opalized dinosaur bone found in the remote Australian Outback. The Winton Formation is a vast layer of fossil-bearing rock spread across central-western Queensland, including the country around the town of Winton.

Formed about 95 to 98 million years ago, it preserves one of Australia’s richest records of dinosaurs. 🦕 Fossils discovered in these rocks include the carnivorous Australovenator and enormous long-necked dinosaurs such as Diamantinasaurus, Wintonotitan, and Savannasaurus.

A fragment like the opalized bone shown here may not contain enough distinctive anatomy to reveal its species, but its location places it among an important group of Australian dinosaur finds. Winton is also part of Queensland’s western opal fields and is especially known for boulder opal formed within ironstone.

08/08/2026

Few decorative stones have patterns as instantly recognizable as ocean jasper. 🌊 Its polished surface may show dots, rings, bull’s-eyes, wavy bands, and rounded patches in colors ranging from mossy green and mustard yellow to cream, rose, rust, and burgundy. No two cuts reveal the same arrangement, and a plain-looking outer surface can conceal a much more dramatic pattern inside.

Ocean jasper is closely tied to Madagascar, particularly the coastal Marovato locality in the country’s northwest. 🌴 The name is a trade term for orbicular material from this area rather than a formal mineral species.

Some specimens contain tiny crystal-lined cavities, while others display dense clusters of circles with crisp borders. Because the pattern changes through a single piece, cutters often study the rough carefully before choosing where to slice it. Strong color contrast, complete orbs, and attractive quartz pockets tend to make polished examples especially desirable.

08/08/2026

Giant amethyst geodes can stand taller than a person and weigh as much as several vehicles. The Guinness record holder weighs about 28,660 pounds and measures about 10 feet long, 6 feet wide, and 7 feet high. 💜

These enormous crystal chambers began as unusually large cavities inside ancient basalt lava flows. As the lava cooled, open spaces remained, and mineral-rich water later moved through cracks in the surrounding rock. Over long periods, layers of agate, clear quartz, and purple amethyst formed along the cavity walls.

The best-known giant specimens come from the Artigas region of Uruguay and Rio Grande do Sul in southern Brazil, both within the vast Paraná volcanic province. ⛏️ Miners often call tall, split-open pieces “amethyst cathedrals” because their pointed interiors resemble narrow chambers lined with violet crystals.

08/08/2026

08/08/2026

Prehnite carries an unusual place in mineralogical history. In 1788, German mineralogist Abraham Gottlob Werner named it for Hendrik von Prehn, a Dutch military officer who had collected specimens in South Africa. 📜

It is widely regarded as the first mineral named after a person, helping introduce a naming tradition that later became common across mineralogy. This practice, however, was not universally liked. In 1813, chemist Richard Chenevix criticized the practice of naming minerals after people and specifically pointed to prehnite as an example.

Instead of forming obvious, sharp individual crystals, prehnite often appears as rounded clusters, bubbly surfaces, fingers, or hemispherical forms. 🍏 Individual prehnite crystals are fairly rare, so it’s more often found in rounded or clustered forms.

07/18/2026

Psiloceras planorbis

Over 100 million years old, discovered in Somerset.

Photo ©️ Geologic Gallery

07/18/2026

70 million year old ammonite fossil embedded in shale ❤

07/18/2026

Wonderstone earns its name from the colorful patterns that run through it like painted ribbons. Much of the best-known material comes from the American West, especially Utah and Nevada, where volcanic ash and silica-rich fluids helped create striking bands of red, cream, brown, yellow, and maroon. 🌋

These patterns are often linked to iron minerals that stained the rock as water moved through cracks and layers over time. Some pieces show soft waves, while others have sharp zigzags, folded bands, or landscape-like scenes.

Wonderstone is usually cut and polished for cabochons, display pieces, beads, and other lapidary work because its designs become much clearer after shaping. ✨ Its relatively fine texture helps it take a smooth polish, which is why slabs often look more vivid than rough pieces picked up in the field.

07/18/2026

This might look like a rock covered in dew, but it's actually covered in tiny botryoidal quartz!

“Botryoidal” describes a surface made of smooth, closely packed bumps that resemble a cluster of grapes. The shape develops when very small quartz or chalcedony crystals grow outward from many nearby starting points instead of forming large, separate crystal points. 💧

Silica-rich water moves through cracks, cavities, or porous rock and leaves thin layers of quartz behind as conditions change. Continued growth builds rounded masses that may overlap and merge across the surface.

Botryoidal quartz is often clear, white, gray, or pale blue, though iron and other minerals can add yellow, brown, orange, or reddish tones. 🔍 Some specimens have a waxy or glassy surface, while others are coated with sparkling drusy crystals.

07/18/2026

Watermelon tourmaline gets its name from its distinctive color zoning, with a pink or red center surrounded by a green outer layer. Some slices also show a thin pale band between the two colors, which makes the resemblance even stronger. 🍉

The colors form as the crystal grows and the chemical conditions around it change. Manganese is linked to the pink tones, while chromium, vanadium, or iron may contribute to the green. Because the colors developed naturally inside the same crystal, no two pieces have exactly the same pattern.

Watermelon tourmaline is often cut into thin slices to display the full color arrangement. It may also be shaped into cabochons, polished freeforms, beads, or faceted gems. 💎 Fine specimens with bright, balanced colors and good clarity are especially prized, though inclusions and internal fractures are common and can add texture to polished pieces.