It is a dark grey metallic mineral which forms acicular prismatic monoclinic crystals. It occurs as colorless to white prismatic hexagonal crystals, typically as acicular radiating groups. It occurs as prismatic to acicular transparent yellow to white orthorhombic crystals. It occasionally occurs as prismatic acicular crystal groups, and individual crystals commonly show twinning. Minerals with an acicular habit include mesolite, natrolite, malachite, gypsum, rutile, brochantite and bultfonteinite. Crystals are short prismatic parallel to the c axis and often acicular. Rutilated quartz is a variety of quartz which contains acicular (needle-like) inclusions of rutile. Crystal appearance (foliated/lamellar (layered), dendritic, bladed, acicular, lenticular, tabular (tablet shaped)). Gypsum flowers are most often acicular, scaly, stellate, and lenticular. Rather, the austempering process forms acicular ferrite and austenite. Individual crystals are rare, but occur as slender to acicular prisms. Tight acicular radiating clusters and sphericules are common forms. The palygorskite component is an acicular bristle-like crystalline form that does not swell or expand. Parapodia with elongate acicular lobes with both acicula penetrating epidermis; neuropodia with a supra-acicular process. Scolecite, like natrolite and mesolite, usually occurs as acicular (needle-like) and fibrous aggregations.