Geyserite is a form of opaline silica that is often found around hot springs and geysers. It is sometimes referred to as sinter. Botryoidal geyserite is known as fiorite.

: a variety of opal that is deposited around some hot springs and geysers in white or grayish concretions.

Hard minerals and rocks are needed to withstand intense heat and pressure. Except for Mammoth Hot Springs, most superheated geyser water passes through rhyolite and volcanic ash and tuff. These rocks consist mainly of silica, a hard mineral found in quartz and glass.

How sinter forms. When high-temperature geothermal fluids reach the surface, they undergo drastic cooling. Much of the mineral material dissolved in these fluids can no longer remain in solution and begins to precipitate as the fluid cools. The most common precipitate is amorphous silica.

Sintering is the process of fusing particles together into one solid mass by using a combination of pressure and heat without melting the materials. Common particles that are sintered together include metal, ceramic, plastic, and other various materials.

Siliceous sinter (geyserite; fiorite) is a deposit of opaline or amorphous silica that occurs as an incrustation around hot springs and geysers and sometimes forms conical mounds (geyser cones) or terraces. The deposition of siliceous sinter is largely due to the action of algae and…

Chert and flint are microcrystalline varieties of quartz. The only difference between chert and flint is color: flint is black or nearly black and chert tends to be white, gray, or pink and can be either plain, banded, or preserve fossil traces.

Most geodes contain clear quartz crystals, while others have purple amethyst crystals. Still others can have agate, chalcedony, or jasper banding or crystals such as calcite, dolomite, celestite, etc. Geodes and geode slices are sometimes dyed with artificial colors.

What You Do:

1. In the beaker, stir 1/2 cup of Epsom salts with 1/2 cup of very hot tap water for at least one minute.
2. Add a couple drops of food coloring if you want your crystals to be colored.
3. Put the beaker in the refrigerator.
4. Check on it in a few hours to see a beaker full of epsom salt crystals!

All you need is a rock and some vinegar to grow either needle-like prisms or branched crystal ferns. The pure mineral is clear or white (aragonite), but you’ll get colored crystals if you grow the crystals onto a rock. While you could eat salt crystals, they aren’t likely as good as rock candy.