Trilobites are a fossil group of extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest known groups of arthropods. The fossils of trilobite are found in a limestone shale. The trilobite is Wisconsin's state fossil.
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide. It is the most important ore of lead and an important source of silver. Galena is the official state mineral of Missouri and Wisconsin.
Agate is a cryptocrystalline variety of silica characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks.
Calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A small amount of manganese is enough to make it glow bright red under some wave lengths of ultraviolet light.
Amethyst is a violet variety of quartz often used in jewelry. Amethyst occurs in primary hues from a light pinkish violet to a deep purple. Amethyst may exhibit one or both secondary hues, red and blue. The best varieties of amethyst can be found in Siberia, Sri Lanka, Brazil and the far East.
