Rectangular Prehnite bead with a central hole, from South Africa. Satin polished finish that catches the light without being mirror-like.
Item details
| Mineral |
Prehnite (calcium aluminum phyllosilicate; Ca₂Al(AlSi₃)O₁₀(OH)₂) |
| Dimensions |
Approx. 17×12 mm face, central hole approx. 2 mm (tolerance ±0.5 mm; see photo for each variant) |
| Shape and back |
Rectangular with slightly rounded edges; axial hole |
| Finish |
Satin polished |
| Hardness |
6–6.5 Mohs — we recommend a closed bezel setting if mounted without hanging; suitable for strung necklaces |
| Origin |
South Africa (high-quality Prehnite deposits in the Northern Cape province) |
| Treatment |
Untreated |
| Item type |
Unique piece: the epidote inclusion pattern varies in each bead |
This specific piece
Prehnite from South Africa is distinguished by the frequent presence of epidote (calcium-aluminum-iron silicate) inclusions in the form of dark green needles or spots within the base apple-green mineral.
The rectangular shape with rounded edges and axial hole makes these beads versatile: they can be strung in series on a necklace, used as a single focal bead, or mounted on a silver pin for a pendant.
How Prehnite is formed
Prehnite is a phyllosilicate that crystallizes mainly in cavities and fractures of basaltic rocks under low-temperature hydrothermal conditions (100–300°C).
What mounting it works for
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Necklace strung on silk or nylon thread — the 2 mm hole accommodates threads up to 1.5 mm; the rectangular beads create a necklace with a different visual rhythm than standard round beads. The apple green pairs well with freshwater pearls or silver beads.
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Focal pendant on a 925 silver pin — a single bead threaded through a headed 925 silver pin and finished with a loop allows it to be used as a pendant; the rectangular format is more unusual than the round for this use.
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Macramé and knots — the 2 mm hole accommodates fine macramé cord; knotting around the bead keeps the translucent green face visible.
Prehnite in lapidary tradition
Although Prehnite is one of the first minerals scientifically identified by name (18th century), its lapidary use became popular from the 20th century when South African deposits began to supply the semi-precious gem market.
The symbolic properties attributed to minerals belong to cultural and historical traditions. They are shared for educational purposes, not as medical advice or a substitute for professional care.
How to recognize genuine Prehnite
Authentic Prehnite shows greenish translucency with areas of greater opacity where epidote inclusions are concentrated; under 10× magnification, dark green needles or spots are randomly distributed.
Frequently asked questions
Is the green color of Prehnite dyed?
No detectable treatment. The green is intrinsic to the mineralogical composition: traces of ferrous iron in the phyllosilicate structure. The darker green spots are natural epidote inclusions.
What thread diameter does the hole accommodate?
The hole measures approximately 2 mm. It accommodates silk or nylon thread up to 1.5 mm, fine memory wire, and 1.5 mm macramé cord.
Can it be bezel-set without using the hole?
Yes: the rectangular format with rounded edges is compatible with a custom-made rectangular 925 silver bezel.
What does the color variation between pieces mean?
The green hue varies according to the concentration of iron and the density of epidote inclusions in each bead. Lighter variants are more translucent; those with more epidote have denser dark green areas.
Are the dimensions exact?
Approx. 17×12 mm with a tolerance of ±0.5 mm. The rectangular shape is produced by lapidary work, not industrial calibration; small variations in angle at the corners are normal.
How to care for Prehnite?
Clean with a soft, damp cloth. No ultrasonics. With a hardness of 6–6.5 Mohs, store separately from quartz and other harder minerals. Consult the jewelry care guide.
See also: cabochon collection · silversmithing materials.
