This pretty combo is cinnabar perched atop a dolomite matrix.
Dolomite is both a mineral and a rock.
The mineral “dolomite” is a pure form of dolomite, an anhydrous (containing no water) carbonate mineral composed of calcium, magnesium, carbon and oxygen. Its chemical composition is most commonly CaMg(CO3)2
Dolomite rock (aka “dolostone”) is a sedimentary carbonate rock composed primarily of dolomite along with impurities such as calcite, quartz and feldspar.
Dolomite rock is found in sedimentary basins worldwide. It is believed to form by the altering of lime mud and limestone deposits by magnesium-rich groundwater.
Cinnabar is a highly toxic mercury sulfide mineral with a chemical composition of HgS.
Years ago, because of its bright red coloring, cinnabar was used as a pigment and carved into jewelry and ornaments. Today, most of that has been discontinued.
Cinnabar (like dolomite rock) also forms by water (hot water and vapors in this case) passing through fractures in rock. Cinnabar most often forms in areas around recent volcanic activity or near hot springs and fumaroles. Fumaroles are openings in a planet’s crust, usually near volcanoes, which emit steam and gases such as carbon dioxide, sulfur dioxide, hydrogen chloride and hydrogen sulfide.
Cinnabar usually forms as coatings on rock surfaces, as fracture fillings and sometimes as deposits in the pore spaces of sediments.
Cinnabar is usually massive in form as opposed to being well formed crystals.
This mercury sulfide often grows with other sulfur minerals such as pyrite, marcasite, realgar and stibnite or with the more common minerals such as quartz, dolomite, calcite and barite