Sommaire pour April 2026 de Rock and Gem

The science of meteoritics is the study of meteors, meteorites and meteoroids. It was born rather dramatically on the afternoon of April 26, 1803, at L’Aigle in Normandy, France. As fireballs flashed across the sky leaving trails of smoke, residents gazed in awe as thousands of rocks plummeted to Earth. Besieged by demands to explain this surreal event, the French Academy of Sciences sent 29-year-old astronomer and physicist Jean-Baptiste Biot to investigate. Biot, the namesake of the biotite mineral group, studied numerous meteorites. He interviewed hundreds of individuals who had witnessed the fall. After confirming that no volcanic activity had occurred anywhere near France on the day of the fall, Biot formally reported that the meteorites had an extraterrestrial origin. This was a daring conclusion that flew in the face…

Visiting a vendor’s booth at a recent gem show, my wife marveled at one of the agates. “Yes, these colors are lovely,” agreed the dealer. “Colors?” asked Nancy. “I’m talking about the bear face!” The dealer looked baffled. “Bear?” Obviously, one of these people is afflicted. The other is not. But afflicted with what? And are you afflicted, too? Let’s find out! WHAT IS PAREIDOLIA? If you see faces, animals, or other images in inert stones, you have pareidolia. This is the psychological phenomenon of seeing patterns with meaning in random inanimate objects. The human mind, it seems, is primed for pattern recognition. Evolutionary psychologists claim this helped us survive in the distant past when we needed to determine quickly whether an approaching face was friendly or angry. It also…

Mammoths of Mexico Rewriting ice age history! It’s described as an Ice Age locality as significant as Rancho La Brea in Los Angeles. It’s north of Mexico City, and its 11,000-16,000-year-old sediments are filled with beasts: saber-toothed cats, dire wolves, camels, horses, ground sloths, and, like La Brea, a lone human nicknamed Yotzin. But here, mammoths take top billing. In the journal Science, articles by journalist Rodrigo Pérez Ortega and a research team led by Eduardo Arrieta-Donato (National Autonomous University of Mexico) describe Mexico’s biggest paleontological discovery, scratched out over three years during airport construction. In a former lakebed, they’ve found more mammoths than have been found to date throughout the tropics. How many? At least 500! Arrieta-Donato’s team analyzed mitochondrial DNA in the bones and found this to be…

Walking in nature, it’s astonishing to notice how plants and rocks intertwine, and equally impressive when a similar design graces public spaces and backyard gardens. Great Falls, Montana, artist Mike Hollern has a knack for incorporating trees and shrubs into rock and metal sculptures, often with a water-feature twist, intertwining these mediums into one-of-a-kind pieces. A lifelong resident of Central Montana, Mike used what was on hand to create practical, yet eye-catching, landscapes. At his first house near the Dearborn River south of Great Falls, he built terraces out of the blocky, igneous rock to create an interesting visual effect. Little did he know, these were the first steps in a lifelong vocation. A CENTRAL MONTANA ARTIST SHAPED BY PLACE The Dearborn River area lies within the 40-mile-long, 20-mile-wide Adel…

With its vivid green color and banding, malachite is one of the most recognizable copper minerals. It has been valued since antiquity and has long been used as a pigment, gemstone and ornamental stone. Malachite famously forms botryoidal (think grapes or tree rings), fibrous, stalactitic, or massive aggregates, as well as distinct crystals or replacing other minerals such as azurite. Formation & Geolo Malachite (Cu2CO3(OH)2) is a relatively soft copper mineral, with a Mohs hardness of about 3.5 to 4, best known for its rich green color and banded patterns. It is a secondary mineral that forms as primary copper sulfides, such as chalcopyrite and bornite, break down through oxidation and chemical weathering. This process takes place near the Earth’s surface, where carbon dioxide–rich waters circulate through copper-bearing rocks and gradually…

Night-sky-colored minerals and gems exhibit captivating colors ranging between Egyptian Blue, Yale Blue, Navy Blue, Midnight Blue and deep violet-blue. These dark, moody and intriguing hues exude a sense of mystery. Reminiscent of a night sky or outer space, these colors appear warm and deep, sometimes with twinkling inclusions of pyrite resembling stars and constellations. These intensely rich colors are perfect for creating dramatic and sophisticated pieces. Very few minerals and gemstones exhibit deep blue, captivating colors that match the night sky. SAPPHIRES & STAR SAPPHIRES Sapphires, the gem variety of corundum, occur in every color of the rainbow. Transparent gemstones are commonly faceted, carved, or cut as faceted beads, while opaque gemstones are mostly cut as cabochons, carved, or cut as beads in many shapes and styles. Some of…

Whether browsing a mineral show, a rock shop, or an online listing, every collector eventually faces the same question: Is this specimen real? The answer is not always as straightforward as it seems. Between synthetics, treatments, repairs, restorations and outright fabrications, the modern mineral market offers a wide spectrum of possibilities. Some are perfectly acceptable; others are less so. It depends on your expectations as a collector. Understanding what “real” actually means is the first step toward buying with confidence. This article explores the many ways minerals are altered, prepared, or enhanced before reaching the display case, and explains how to recognize these common practices. More importantly, it will help you decide what falls within your own definition of acceptable. Ultimately, that judgment belongs to you. WHAT IS “REAL” AND…

Black calcite is the term used to describe black to dark gray calcite or aragonite found in many silver mines in the western United States. The material is commonly found in veins and has curved and somewhat rhombic cleavage. The black color is because of dispersed grains of manganese oxide, and it often contains small amounts of additional minerals such as zinc, lead and silver. Black calcite is common in many of the mining districts in southwest New Mexico, especially near former silver mines in carbonate rocks associated with Tertiary-age volcanics. The Petroglyph Mine, also known as the Miners Dream Mine, has excellent examples of black calcite. BLACK CALCITE Black calcite (CaCO3) has an interesting appearance and is an important indicator mineral for other metals. For instance, silver deposits are…