Polyhedroid Agates
SpiritRock Shop
Click on any photo to see a larger version
Museum Specimens
Official PayPal Seal
                  (center top specimen photo from 2009 Gem Shop Calender)
Polyhedroid Agates are one of nature’s great unexplained formations. These geometric beauties were only found for a short time in
the 1970’s and only in one location in the world. It is fitting that some of the most desirable agates in the world come from the
greatest agate producing country, that being Brazil. These were located in Paraiba the only state in Brazil that ever produced any of
these specimens. These stunning agates formed in geometric pattern shapes rather than the more common round or oval agate
shape. The theories of formation of these agates are still an ongoing evaluation among geologists. The most agreed upon formation
theory seems to be that the sharp geometric shapes are thought to have been formed in the voids between interlaced crystals of
Barite, or possibly Calcite crystal formations.
The agate nodules can be solid or hollow and the best grades have distinct, colorful fortification agate bands that follow the typically
triangular or trapezoidal shape of the Polyhedroid Agate. They are some of the highest quality agates available, and are able to be
polished to the highest mirror glaze finish that quality agates can obtain. These agates rarely have fractures or other imperfections.
Most nodules are quartz with black, gray, white being the predominant colors of the Polyhedroid agates. Shapes can be a variety of
geometric forms with the equilateral triangle shape being the most desirable shape. (One cannot help but wonder if Euclid, the
father of Geometry found some of these agates or maybe nature made these just to prove Euclid’s theorems.) The Polyhedroid
Agate makes the best agate show piece and conversation piece in any collection. These are very rare and expensive….but like they
say…”You get what you pay for!”  Polyhedroid Agates are our favorites!
Polyhedroid Slab from Paraiba Brazil
Beautifully polished face! This exciting piece is from our polyhedroid collection. This amazing piece has clear
crackle appearance quartz with a black-grey band in the center of the quartz band. The interior vug
chalcedony forms to a stunning botryoidal interior.

This specimen weighs 7oz  (199g)
and measures 5.2 x 2.9 x 0.6 to 0.37 inches (134 x 75 x 15 to 9mm)
Piece has one natural fracture
Item # PHA04143932
Polyhedroid Agate Slab with
Black Outlined Botryoidal Vug
We have spent the better part of the last 14 years procuring Polyhedroid
specimens from all over the world. We Have sold a few polished ones from time to
time. As we get older we are realizing that we probably will never be able to cut
and polish all the wonderful Polyhedroid Agates we have collected, so we have
decided to sell off a large portion of what we have collected.

We will be listing here three or four wholesale priced large #2 Polyhedroid Agates
which are geometrically shaped, mostly with quartz centers, but can have small
agate banding in the center. These will be sold at current wholesale bulk pricing
which is now $9.00/lb. We will also be listing some smaller good to AA grade
(Jewelry grade) agates. These can sell priced on current market.

When these agates are light colored on the outside, the interior will mostly be
clear quartz. The amount of darkness in the exterior skin will give you an idea of
how much grey or black shading is inside these rare agates. If you look at the
photos above and at our listings you will see the wide array of possibilities for the
interiors of these agates. You never know until you cut one open what surprises
lie hiding inside. We have always been fascinated with Brazilian Agates and we
feel very lucky to have some to offer you for your collection and for you to cut and
polish.

We have also come across a matrix specimen which shows the Polyhedroid agate
formation in crystalline calcite, supporting the current best formation theories. You
can see the calcite blades and agate shapes pointed out with the arrows in the
photo shown on the left.  

This specimen was photographed wet and has had the contrast increased
and has been darkened to better show the polyhedroid agate formations
and calcite plate formations in this face cut matrix specimen from Paraiba
Quadrilateral Polyhedroid Agate Slab from Paraiba Brazil
This is a Quadrilateral (4 straight sides) Polyhedroid Agate Slab from our collection. This piece is not polished and is
shown wet and dry. It has some nice inclusions and a nice drusi quartz lined center
This specimen weighs 1 oz (30g) and measures 3.4 x 1.8 x 0.19 inches (88 x 47 x 4.9mm)
Item # 16PHAS04140630
Quadrilateral Polyhedroid Agate Slab (Not Polished)
Quadrilateral Polyhedroid Agate Slsb from Paraiba Brazil
This is a Quadrilateral (4 straight sides) Polyhedroid Agate Slab from our collection. This piece is not polished and is
shown wet and dry. It has the preferred black inner color and has a botryoidal chalcedony lined center
This specimen weighs 1.6 oz (46g) and measures 3.9 x 2.4 x 0.20 inches (100 x 62 x 5.2mm)
Item # 17PHAS04142550
Quadrilateral Polyhedroid Agate Slab (Not Polished)
Polyhedroid Specimen from Paraiba Brazil
This is a Polyhedroid Agate Nodule from our collection. This piece has been cut and has one surface polished. It is
shown dry. It is clear with black accents and has a botryoidal chalcedony lined center
This specimen weighs 3.3 oz or 0.2 lb (94g) and measures 2.7 x 2.5 x 1 inches (6.8 x 6.5 x 2.5cm)
Item # 18PHAS04148211
Polyhedroid Agate Nodule with one Surface Polished
Polyhedroid Agate Nodule from Paraiba Brazil
This is a Polyhedroid Agate Nodule that has one face cut that has been sealed. This old stock piece was procured from
an old rock shop in Arizona. This piece could produce a couple of nice slabs or makes a classic old stock display.
This specimen weighs 5.5 oz or 0.34 lb (155g) and measures 2.1 x 1.9 x 1.9 inches (53 x 50 x 49mm)
Item # 20PHA04147892
Polyhedroid Agate Nodule
Pentagonal (5 sides) Polyhedroid Agate Rough Nodule from Paraiba Brazil
This is a rough Polyhedroid Agate Nodule that has been cut.  Shown dry, it looks normal. When shown wet, a lavender color is visible.
This may be due to the presence of manganese, while others have suggested that the amethyst color could be from ferric
thiocyanate or sulfur found in amethyst stones. The interior is a botryoidal chalcedony. This is an Exceptionally Rare Polyhedroid
specimen. We have never seen or heard of another specimen like this.
This specimen weighs 2.6 oz or 0.16 lb (74g) and measures 2.4 x 1.2 x 1 inches (62 x 31 x 26mm)
Item # 22PHA04149993
Exceptionally Rare Polyhedroid Agate
Rough Nodule with Quartz and Amethyst
Crystalline Formation

$129.00
Quantity Available 1 each
Polyhedroid Agate Nodule from Paraiba Brazil
This is a Polyhedroid Agate Nodule that has one face cut that has been sealed. This old stock piece was procured from
an old rock shop in Arizona. This piece could produce some nice slabs or makes a classic old stock display.
This specimen weighs 4.5 oz or 0.28 lb (128g) and measures 2.1 x 1.8 x 1.5 inches (53 x 47 x 39mm)
Item # 21PHA04148892
Polyhedroid Agate Nodule
Polyhedroid Agates in Matrix from Paraiba Brazil
This is the specimen we picked up years ago. It is a piece of the matrix from Paraiba, Brazil. When it was cut, a few
Polyhedroid Agates become visible. The specimen was sealed on the cut face to preserve the integrity of the agate
formation in calcite blade structure. This is the specimen we show at the top of this page.
This specimen weighs 5.7 oz or 0.35 lb (161g) and measures 3 x 1.75 x 1.3 inches (78 x 44 x 35mm)
There is a quadrilateral (almost trapezoidal) agate who's face measures 2.1 x 0.7" (53 x 18mm) and a small kite like
agate that measures 19.5 x 5.9mm easily seen in the photos.
Item # 23PHA04146551
Polyhedroid Agates in Matrix
Photographed Dry
Photographed Wet
Polyhedroid Display Specimen from Paraiba Brazil
This is an Extra Large 1.81 lb "Old Stock" piece from our collection. This was cut and polished in our shop. There is a
nice Triangular Crystalline Face with a small center agate lined vug with drusy quartz crystals inside. This piece shows
the 3 pattern seams in the crystal from the inner triangle vug to the outer skin points. The crystal face also indicates a
possible darker center fill deeper in the agate. This agate has natural angles on the sides which allow for three different
90 degree face displays or about 45 degrees on the back which makes this one a nice natural display specimen. This
could also be cut into slabs  
The photos show its different faces and angles.
This specimen weighs 28.9 oz or 1.81 lb (822g)
and measures 4.3 x 3.3 x 3.6 to 1.9 inches (11 x 8.4 x 9.2 to 4.9cm)
Item # 1PHA121605201
Rare Old Stock P
olished Face
Polyhedroid Agate D
isplay Specimen

$295.00
We are currently working on cutting and polishing some more
Polyhedroid Agates. Some for display and some Jewelry Grade
Polyhedroids. We will be listing them in late February or early
March of 2017
Cut and Polished in our
Work Shop!