Dioptase: Dioptase is a relatively rare emerald-green mineral, sometimes tinged bluish or blackish. Crystals are small with a vitreous luster, and is transparent to translucent. Its green is very strong and bright even when compared to the more subtle green of emerald. It forms green to blue-green encrustations and fillings of enamel-like or earthy texture. It is uncommon, and found in the weathered zone (read full)

Meerschaum: Meerschaum is a clay-like hydrous magnesium silicate. It has no crystals, and occurs as earthy aggregates, porcellanous masses, nodular, and porous. In the fresh state it is soapy and soft, but hard when dried. It sticks to the tongue and its taste sets the teeth on edge. It is opaque, has flat conchoidal, earthy fracture, and an orthorhombic microcrystalline system. Because of its high porosity (read full)

Chrysocolla: Chrysocolla is a silicate that forms as stalactitic masses, in radiating groups, or closely-packed aggregates. It appears as green, blue, and blue-green, but can also be brown or black when impurities are present. It may be translucent to nearly opaque, and has a vitreous to earthy lustre. It forms in the oxidation zone of copper deposits, and occurs with azurite, malachite, and cuprite. When d (read full)

Cerussite: Cerussite is a colorless carbonate of the aragonite mineralogical classification. It appears as colorless or white crystals with grayish tints, elongated and generally twinned to form a reticulated network with 60-degree angles, as stubby, tabular crystals in star- or heart-shaped twins. It can also be grey, greenish, or blue as a result of inclusions, such as lead, or copper. Impure cerussite is (read full)

Staurolite: Staurolite is a hydrous magnesium aluminum silicate that crystallizes in the monoclinic system. It appears as coarse, dark gold-brown prisms, or sometimes reddish-brown to black stubby crystals. On weathered rock, it stands out in contrast like sand-coated yellowish brown prisms. Surfaces are often rough or covered with an earthy coating because of natural alteration. It frequently occurs in ch (read full)

Smithsonite: Smithsonite is a mineral in the group of Nitrates, Carbonates, Borates, with a hexagonal crystal system. It appears uncommonly in rhombohedral or scalenohedral crystals. But most of the time it appears with curved faces, like a thick creamy aqua-green mixture poured on rock and left to aggregate in clusters shaped like bunches of grapes, rounded, kidney-like, or to form like elegant icicles, and (read full)