South Dakota  Symbols, Mineral: Rose Quartz

Adopted in 1966.

Rose quartz, mined in the southern Black Hills, is the state mineral. It was discovered near Custer in the late 1880s. It is used primarily for ornaments and jewelry.

Quartz is a very common mineral and made of silicon (Si) and oxygen (O) combined together as SiO2. There is many varieties of the quartz family found in nature. All varieties of quartz have essentially the same chemical composition and crystalline structure. The differences is in the method of formation, the grain size, and the impurities in the mineral, which give rise to varying colors and color patterns. Quartz is generally transparent to translucent. Agate is one type of quartz. Most quartz can be characterized by its glass-like appearance, its conchoidal fracture pattern, and its relative hardness.

Rose quartz is light to darker rose or pinkish-colored quartz due to small amounts of the element titanium. Most rose quartz is coarsely crystalline. The crystals usually do not have external faces because of interference from other growing crystals. In South Dakota, the color of rose quartz ranges from pale shades of pink to rose-pink to rose-red. Occasionally it has a faint purplish or lavender cast. Rose quartz from certain localities in South Dakota exhibits distinct asterism. Asterism refers to a rayed or star-shaped figure of light on the surface of a mineral sample. If a rose quartz sample exhibits asterism, it is called star rose quartz. Usually star rose quartz can only be seen on cut and polished pieces of rose quartz. It is virtually impossible to recognize asterism in an unpolished specimen.

How is Rose Quartz Form?

Rose quartz is an igneous mineral that originates deep within the earth's crust and is forms from the solidification of granitic magma. Within the earth, huge masses of magma slowly migrate upward toward the surface of the earth. Magna is driven upward because magma is less dense than surrounding solid rock. In time, the magma s cool off and solidify. Magma generally solidify miles beneath the earth's surface except for volcanoes and volcanic rocks which are formed by magma that erupts, producing lava flows. Near the end of its upward migration, the magma temperature has been lowered. Some of the magma has crystallized into solid minerals. The fluid magma remaining near the fringe tends to be rich in volatiles, water, silica, oxygen, and some other elements. This magma may squirt and intrude into the surrounding and overlying rocks, fingering outward from the main mass of the magma along zones of weakness or fractures. As the molten rock in these intrusions continues to slowly cool, rose quartz crystals may begin to form. Quartz crystals will continue to form and grow larger until all the magma has crystallized.

Where Found?

In South Dakota, rose quartz is found in pegmatites in the Southern Black Hills area. These pegmatites are associated with the Harney Peak granite mass now exposed because of erosion. These pegmatite s formed during the Precambrian era, and are about 1,700 million years old.