Pseudomorphs occur when one mineral replaces a second mineral, molecule by molecule, so that the shape (including any crystals) of the second mineral are faithfully reproduced. Petrified wood is a type of pseudomorph, as indeed are fossils, since the original organic carbon has been replaced, often by silicates or carbonates.
Malachite ps Barite from 2001, ex Linda St-Cyr $125
This was a one-time find in 2001, an unusual pseudomorph. The photo on the right shows the bottom of the specimen, which evidentially grew up against a flat rock and exhibits some long, grassy-looking Malachite crystals.
Quartz & Fluorite ps Stibnite $48
The back of this specimen (right-hand photo) is all Fluorite, but on the other side, several roughly cylindrical structures are seen. The two largest form a backwards "L" in the left-hand photo. These are the pseudomorphs of Stibnite.
Siderite & Quartz ps Aegerine, ex Linda St-Cyr $45
Mont Saint-Hilaire is famous for many rarities and pseudomorphs. This specimen is a very detailed pseudomorph of a pair of Aegerine crystals with two small Smoky Quartz crystals and some tan Siderites attached. It is relatively large for a Mont Saint-Hilaire pseudomorph, and it is unusual also in the minerals involved.
Ancylite-(Ce) accounts for many of the pseudomorphs that are found at Mont Saint-Hilaire. Ancylite-(Ce) can be recognized by its lavender-pink color under tungsten lighting and green color under fluorescent lighting, as in the photos above. The tiny reddish crystals are Rhodochrosites.
Endlichite ps Wulfenite, ex Linda St-Cyr $95 SOLD
This piece looks like an epimorph - a special type of pseudomorph where the replacement mineral becomes a coating over the original. The original often, but not always, dissolves. (If the original dissolves, the pseudomorph can also be called a cast.) I particularly like the way in which the prismatic Endlichite grows perpendicular to the original Wulfenite blades, making them into spiky replicas of what they once were.
Siderite ps Calcite on Pyrite, Sphalerite and Quartz $225
The matrix consists of a layer of bright cubic Pyrite dotted with Sphalerite and Quartz, then a layer of cream-colored rock matrix, then another layer of Pyrite, the overall effect being of an ice-cream sandwich topped by a scoop of coffee ice cream. Michael Shaw in MinDat.org wrote, "These curved rhombs which resemble clam shells are the least common of the three forms of siderite pseudomorphs of calcite from the Turt Mine." This piece attracts a great deal of attention because it is large, bright and curiously shaped.
Quartz & Lepidolite ps Tourmaline $65
The unusual thing about this pseudomorph is that it has been preserved mid-way during the process of forming a pseudomorph, and the Quartz is replacing the inside of the Tourmaline first, leaving a shell of bright, transparent green Tourmaline through which the Quartz can be viewed.
Hematite ps Magnetite ("Martite")
A nice sharp pseudomorph classic, known as "Martite".
Meyerhofferite (TL) ps Inyoite $35
An interesting and sharply formed pseudomorph from the Type Locality of Meyerhofferite. The radial patterns of the Meyerhofferite are pressed into the blocky form of the Inyoite - most visible in the larger version of the left photo - perfectly illustrating the effects of pseudomorphism.
Tincalconite ps Borax, ex Linda St-Cyr $65
The sharpness of this pseudomorph is almost unbelievable. The Tincalconite is very light and delicate.
Malachite(?) ps Petrified Wood, ex Linda St-Cyr $65
This was one of the first mineral specimens in my collection. I thought I knew what petrified wood looked like, but this piece showed me that the mineral world had many surprises waiting for me. Although it was sold to me as Malachite, most references (like MinDat.org) say that green petrified wood is actually Chromium- or Vanadium-rich petrified wood.
Rutile paramorph of Brookite $95
A paramorph is a pseudomorph of one mineral by one of its dimorphs. In other words, the original mineral (in this case, Brookite, which is TiO2) and the pseudomorph mineral (Rutile, also TiO2) have the same chemical formula but different molecular structures. Magnet Cove is quite famous for this particular paramorph. The pseudomorph on the specimen is actually much easier to see in person than in the photos .
Turquoise ps Apatite $18
These are very famous though somewhat crude pseudomorphs.
Goethite ps Pyrite $20
A very fine example of a classic pseudomorph from the most famous US locality for Goethite ps Pyrite.
Talc ps Antigorite fans, ex Linda St-Cyr $15
The fans of the Antigorite are very clearly visible, well reproduced in the Talc. A very interesting and unusual pseudomorph.
GAL9-8 Galena (var. Plumbeine) ps Pyromorphite, Wheal Hope, Cornwall, England, UK $44
MAL9-11 Azurite & Malachite ps Azurite, Remolinos Mine, Chile $26
HPS7-3 Hematite ps Siderite, Lake George, Park Co, Colorado $25
Also, my husbands website:
has more pseudomorphs:
Muscovite ps Spodumene with Feldspar, Ouro Fino Mine,
Gypsum with Sand inclusions, Ahahrani, Saudi Arabia $25
H-024 Hematite ps Siderite, Lake George, Park Co, Colorado $40
or select a gallery from the table below:
Questions? Please send me an email.
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