Upcoming Rockhounding Events in South Dakota

Rose Quartz

Streak: White

Hardness: 7

Chemical Formula: SiO2

South Dakota is known for Rose Quartz, a pink variety of quartz that may feature diasterism, or star-like shape of light when illuminated from behind when shaped and polished.

Quartz is one of the most common minerals found in the Earth’s crust. While it is usually colorless and transparent, quartz can also be found in a wide variety of colors and a range of opacity. These varieties generally have their own name such as rose quartz, amethyst, smoky quartz, and citrine.

Quartz can also be found in cryptocrystalline varieties, or quartz that is made up of microscopic crystals. These varieties include chalcedony, agate, and jasper.

Photo: Mineral Cuarzo Rosa by Luis Miguel Bugallo Sánchez is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Agate

Streak: White

Hardness: 7

Chemical Formula: SiO2

Agate is a common form of chalcedony, a microcrystalline form of quartz. It’s banded, colorful appearance has lead to its widespread use throughout human history.

Most varieties of agate are named for its visual appearance, such as fire agate which has inclusions of red or brown hematite. Agate can also vary in its banding appearance, some agates have a dendritic habit or lace-like patterns with eyes, swirls, and other patterns.

Because this mineral is a form of quartz, it’s hardness lends itself to uses not commonly associated with such visually appealing minerals. Agate has been used to create precision pendulums, mortars and pestles, and fine knife-bearing edges for laboratory balances.

Photo: Agate by James St. John is licensed under the Creative Commons Attribution 2.0 Generic license.

Petrified Wood

Petrified wood forms when plant debris is buried by sediment and then replaced by deposition of mineral material dissolved in groundwater.

Photo: Petrified Wood by Diego Delso, delso.photo, License CC-BY-SA

Gold

Streak: golden-yellow

Hardness: 2.5 – 3

Chemical Formula: Au

Gold generally occurs in tree-like growths or grains. Because of it’s inert state, gold resists tarnish and is generally found in a relatively pure form.

Almost all of the gold recovered from the earth comes from placer deposits, weathered particles concentrated in river gravel. This relatively rare mineral has been used since antiquity in many facets of human life from coinage to art and beyond.

Today, 10% of the gold produced finds its way into industry with much of it being used to produce electronic components.

Photo: Gold by Robert M. Lavinsky is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

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Celeste
Author: Celeste

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