Anthodites ( Greek ἄνθος ''ánthos'', "flower", ''-ode'', adjectival combining form, ''-ite'' adjectival suffix) are
speleothem A speleothem (; ) is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on ...
s (cave formations) composed of long needle-like crystals situated in clusters which radiate outward from a common base. The "needles" may be quill-like or feathery. Most anthodites are made of the mineral
aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including p ...
(a variety of calcium carbonate, CaCO3), although some are composed of
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
(CaSO4·2H2O). The term ''anthodite'' is first cited in the scientific literature in 1965 by Japanese researcher N. Kashima, who described "flower-like dripstone" composed of "an alternation of calcite and aragonite".

Structure, composition and appearance

The individual crystals of anthodites develop in a form described as "acicular" (needle-like) and often branch out as they grow. They usually grow downward from a cave's ceiling. Aragonite crystals are contrasted with those made of calcite (another variety of calcium carbonate) in that the latter tend to be stubby or dog-tooth-like ("rhombohedral", rather than acicular). Anthodites often have a solid core of aragonite and may have huntite or
hydromagnesite Hydromagnesite is a hydrated magnesium carbonate mineral with the formula Mg5(CO3)4(OH)2·4H2O. It generally occurs associated with the weathering products of magnesium containing minerals such as serpentine or brucite. It occurs as incrustation ...
deposited near the ends of the branches. Anthodite crystals vary in size from less than a millimeter to about a meter, but are commonly between 1 and 20 millimeters in length.


Anthodites may occur sporadically throughout some limestone caves, but may be spectacularly abundant in others, with clean white crystals growing all over the calcite or other rock surfaces. Examples of sites with abundant anthodite displays include Carlsbad Caverns, Craighead Caverns, Skyline Caverns in the United States and the Grotte de Moulis in France.


Among the "quill-like" varieties of anthodite is sometimes included the "sea urchin-like" formation known as '' flos ferri'', although othersShaw, T. (1992), ''History of Cave Science: The Exploration and Study of Limestone Caves to 1900'', 2nd ed., Sydney Speleological Society, Broadway, NSW, Australia. have considered them a slender variety of helictite. Among the "feathery" varieties of anthodite is " frostwork", a type of speleothem consisting of "bushes" of fine acicular aragonite crystals in radiating clusters. Their appearance is often compared to that of a cactus or thistle plant. In its composite
stalagmite A stalagmite (, ; from the Greek , from , "dropping, trickling") is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically co ...
form, frostwork may possess spiny limbs like a miniature fir tree. The term was first used by cave guides at Wind Cave in South Dakota, USA, during the 1890s to describe speleothems which looked like ice "frostwork".

Anthodite-like formations

* Helictites are curved or angular twig-like lateral projections of calcium carbonate, which appear to defy gravity. Rather than radial clusters, helictites often occur in tangled masses. The "twigs" have a tiny central canal. * Cave flowers (also known as "gypsum flowers" or "oulopholites") consist of gypsum or epsomite. In contrast to anthodites, the needles or "petals" of cave flowers grow from the attached end. * Cave cotton (also called "gypsum cotton") is very thin, flexible filaments of gypsum or epsomite projecting from a cave wall.