outbreak of goosebumps from the crypt
Botryoidal specimen of cryptomelane on goethite from Ironwood, Gogebic County, Michigan, USA, on display at the AE Seaman Mineral Museum, Michigan Technological University, Houghton.
Cryptomelane is a near-surface manganese mineral formed during the weathering of manganese-bearing iron oxide-rich rocks. This grey beauty is actually two minerals. The bubbly grey stuff is cryptomelane which is composed of 1 potassium + 8 manganese + 16 oxygen molecules. Goethite is the rusty brown underlying plate of iron oxide.
"Supergene" or "alteration" or "secondary" minerals are the fun stuff, because they form unusual or colorful or beautiful specimens. The word "supergene" is used to describe conditions of low-pressure and low-temperature during "weathering". The Low-P (pressure) and low-T (temperature) supergene minerals form in near-surface conditions versus High-P and High-T minerals formed deeper in the Earth's crust. Alteration by element-rich near-surface water will form new hydrated (supergene) minerals. Such mineral-forming alteration is time-, place- and element-specific. And instead of being eroded, carried away and recycled, some altered rock formations may be subsequently buried and preserved if in a sedimentary environment.
= Primary Rock-Forming Minerals versus Secondary Minerals =
The rocks in the Earth's crust consist of 12+ primary minerals.
The remainder of ongoing identification of 6000+ minerals (MINDAT website) are all of the other elements in the periodic table kept busy throughout time combining and recombining with primary rock-forming minerals.
The 12+ primary rock-forming minerals form the floating granite-dominated continents comprising 30% of Earth's surface, whereas the basalt-dominated ocean bottom crust is the hidden 70%. Perhaps 500+ minerals have some abundance on Earth out of 6000+ known minerals. Which means most minerals are extremely rare, usually tiny in size and mostly seen by microscope or identified/characterized by scanning electron microscope (SEM).
So a hand-sized supergene mineral specimen is very cool !!
outbreak of goosebumps from the crypt
Botryoidal specimen of cryptomelane on goethite from Ironwood, Gogebic County, Michigan, USA, on display at the AE Seaman Mineral Museum, Michigan Technological University, Houghton.
Cryptomelane is a near-surface manganese mineral formed during the weathering of manganese-bearing iron oxide-rich rocks. This grey beauty is actually two minerals. The bubbly grey stuff is cryptomelane which is composed of 1 potassium + 8 manganese + 16 oxygen molecules. Goethite is the rusty brown underlying plate of iron oxide.
"Supergene" or "alteration" or "secondary" minerals are the fun stuff, because they form unusual or colorful or beautiful specimens. The word "supergene" is used to describe conditions of low-pressure and low-temperature during "weathering". The Low-P (pressure) and low-T (temperature) supergene minerals form in near-surface conditions versus High-P and High-T minerals formed deeper in the Earth's crust. Alteration by element-rich near-surface water will form new hydrated (supergene) minerals. Such mineral-forming alteration is time-, place- and element-specific. And instead of being eroded, carried away and recycled, some altered rock formations may be subsequently buried and preserved if in a sedimentary environment.
= Primary Rock-Forming Minerals versus Secondary Minerals =
The rocks in the Earth's crust consist of 12+ primary minerals.
The remainder of ongoing identification of 6000+ minerals (MINDAT website) are all of the other elements in the periodic table kept busy throughout time combining and recombining with primary rock-forming minerals.
The 12+ primary rock-forming minerals form the floating granite-dominated continents comprising 30% of Earth's surface, whereas the basalt-dominated ocean bottom crust is the hidden 70%. Perhaps 500+ minerals have some abundance on Earth out of 6000+ known minerals. Which means most minerals are extremely rare, usually tiny in size and mostly seen by microscope or identified/characterized by scanning electron microscope (SEM).
So a hand-sized supergene mineral specimen is very cool !!