4 天之前 · A very rare and impressive large pseudomorph combination from the famous mines at Dalnegorsk. Hematite has replaced a striking, extremely large blocky, tapered, parallel-growth, terminated ilvaite crystal. The 360-degree pseudomorph is sheathed in tiny, sparkly, gemmy, rust-brown siderite rhombs.

It also occurs in fibrous to compact masses, sometimes with botryoidal surface (photo in margin). More rarely it can replace octahedrons of magnetite, called hematite pseudomorph after magnetite (or martite). In very rare cases the crystals may be prismatic identical to those of the corundum with which it shares an identical crystalline structure.

2018年12月29日 · As larger masses, it may be botryoidal, mammilary, reniform, oolitic, radiating, stalactitic, or simply massive. As well-shaped crystals, it may present as scalenohedral, rhombohedral or tabular crystals. Rarely, dendrites and rosettes are recognized. On occasion, it will form a pseudomorph after octahedral crystals of magnetite.

Branching stalactites and botryoidal masses, often associated with bright contrasting Vanadinite, come from the Four Man Mine, Taouz, Morocco. Recent finds of branching Goethite pseudomorphs after Marcasite are exceptional at the Farfara Oasis, in the White Desert of Egypt.

In this gallery, a specimen is also labeled hematite after pyrite ? from the Brézouard. This is no pseudo either. De crystal form is hexagonal and is just another type of another vein.

2019年5月30日 · Hematite is hexagonal. Combined with the OH radical, it forms goethite, hydrous iron oxide, and when hematite forms a pseudomorph after magnetite, we call it martite. Hematite with its different crystal forms in the hexagonal system is deserving of serious collecting.

2024年2月25日 · Quite a few common minerals show this pattern on occasion. Generally twinned crystals closely resemble each other, but some of the odder forms of twinning like merohdral twinning, are a bit harder to recognize since they can collide on multiple planes. Penetration twinning is a particularly interesting manifestation.

Botryoidal, reniform, and mammillary forms of hematite are known as “kidney ore” or “kidney iron.” “Rainbow hematite” is iridescent, while a crystalline, silvery-gray, lustrous, often micaceous form is known as “specularite” or “specular hematite,” marketed in Alaska as “black diamond.”

Common goethite pseudomorphs include pyrite, siderite, and marcasite, though any iron(II)-bearing mineral could become a goethite pseudomorph if proper conditions are met. It may also be precipitated by groundwater or in other sedimentary conditions, or form as a primary mineral in hydrothermal deposits.

Botryoidal Hematite forms when hematite crystals grow in a radiating, spherical pattern, creating rounded, overlapping masses. This distinctive growth habit can occur in a variety of geological settings, including sedimentary deposits and hydrothermal veins.