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A Petoskey stone is a rock and a fossil, often pebble-shaped, that is composed of a fossilized rugose coral, Hexagonaria percarinata. [1] Such stones were formed as a result of glaciation, in which sheets of ice plucked stones from the bedrock, grinding off their rough edges and depositing them in the northwestern (and some in the northeastern) portion of Michigan's lower peninsula.
In the 1960s, archaeologists digging at the site found caves with artifacts left by hunter-gatherers 12,000 years ago, during the last Ice Age. A Paleo-Indian fluted point, a very rare stone tool, was among them.[1] At the time of its discovery it was the oldest such site east of the Mississippi.[2]
Amethyst crystals – a purple quartz Apophyllite crystals sitting right beside a cluster of peachy bowtie stilbite Aquamarine variety of beryl with tourmaline on orthoclase Arsenopyrite from Hidalgo del Parral, Chihuahua, Mexico Aurichalcite needles spraying out within a protected pocket lined by bladed calcite crystals Austinite from the Ojuela Mine, Mapimí, Durango, Mexico Ametrine ...
In 1986, California named benitoite as its state gemstone, a form of the mineral barium titanium silicate that is unique to the Golden State and only found in gem quality in San Benito County. [ 80 ] ^ Colorado is the only state whose geological symbols reflect the national flag's colors: red (rhodochrosite), white (yule marble), and blue ...
Evaporite – Water-soluble mineral deposit formed by evaporation from an aqueous solution; Flint – Cryptocrystalline form of the mineral quartz; Geyserite – Form of opaline silica often found around hot springs and geysers; Greywacke – Sandstone with angular grains in a clay-fine matrix; Gritstone – Hard, coarse-grained, siliceous ...
Ice, mercury (low melting point); allophane, delvauxite, hisingerite (amorphous/ poorly crystalline); actinolite, augite, omphacite, sanidine (intermediate member of a solid solution series) are IMA/CNMNC valid names too. The reasons can be inherited pre-IMA status, practical reasons or entrenchment in the literature, including medical and ...
The term rock formation can also refer to specific sedimentary strata or other rock unit in stratigraphic and petrologic studies. A rock structure can be created in any rock type or combination: Igneous rocks are created when molten rock cools and solidifies, with or without crystallisation. They may be either plutonic bodies or volcanic ...
A ventifact (also wind-faceted stone, windkanter [1]) is a rock that has been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals. [2] The word “Ventifact” is derived from the Latin word “Ventus” meaning ‘ wind ’.