Reniform and stalactitic masses with a radiated fibrous structure also occur.
As crystals, and as stalactitic, encrusting, reniform, massive, earthy and occasionally pulverulent forms as "sulphur meal."
The Vavau group consists entirely of coral limestone, which is occasionally crystalline, and contains stalactitic caves of great beauty.
Well developed crystals are extremely common, but the mineral occurs also in a granular, earthy, or stalactitic condition.
The commonest state of aggregation is that of radially arranged fibres, the external surface of the mass being globular, nodular or stalactitic in form.
It is never crystallized, but may have a fibrous or microcrystalline structure, and commonly occurs in concretionary forms or in compact and earthy masses; sometimes mammillated, botryoidal, reniform or stalactitic. The colour presents various shades of brown and yellow, and the streak is always brownish, a character which distinguishes it from haematite with a red, or from magnetite with a black streak.
Deposits of limonite in cavities may have a rounded surface or even a stalactitic form, and may present a brilliant lustre, of blackish colour, forming what is called in Germany Glaskopf (glass head).
By modern mineralogists the name chalcedony is restricted to those kinds of silica which occur not in distinct crystals like ordinary quartz, but in concretionary, mammillated or stalactitic forms, which break with a fine splintery fracture, and display a delicate fibrous structure.
Very fine examples of stalactitic chalcedony, in whimsical forms, have been yielded by some of the Cornish copper-mines.
The stalactitic display exceeds that of any other cavern known.
Hence some stalactites have their tips under water long enough to allow tassels of crystals to grow on them, which, in a drier season, are again coated over with stalactitic matter; and thus singular distortions are occasioned.
Thus in the microcrystalline chalcedony the lustre is waxy, the fracture fibrous to even, and the external form botryoidal or stalactitic flint and chert are compact and have a splintery fracture: jasper is a compact variety intermixed with much iron oxide and clay and has a dull and even fracture.
Amid walls wonderfully draped with stalactitic tapestry.
There are some fine stalactites near this pit, and others in the Fairy Grotto and in Pensico Avenue; but, considering the magnitude of Mammoth Cave, its poverty of stalactitic ornamentation is remarkable.