The Gonabad Thunder's Eggs

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Gonabad thunder's egg field, Gonabad, South Khorassan Province


Gonabad thunder’s egg field situated in 12km north-northwest of Gonabad city, in South Khorassan province, east of Iran. The geology of area composed of a vast volcanic sequence with rhyodacitic to andesite-basaltic composition which shows a continental volcanism with acidic to intermediate term. This volcanic sequence is late to early-middle Eocene in age based on K-Ar dating which has been done during geological surveying in 1:250000 scale and revealed 51.6 to 54.8 MY age for this volcanic rocks.

The intense weathered hills which covered with broken volcanic rocks formed the common sight of this area. Surface of the hills is covered with many loose nodules of thunder’s egg which mostly broken. They are purple to red in color and have a mean diameter between 5 to more than 40 cm. Some exploratory diggings have been done for exploration agate reservoirs by Gowhartarashan-e-Shargh Company. It is not so far from exception that their exploratory operation had not hopeful results.  Nodules are mostly filled with quartz crystals and are thunder’s egg geodes which are far from their exception.

Most of nodules basically are filled with quartz crystals, so called “frozen” and have not commercial value. The others are mostly thunder’s egg geodes with little central void. They are look like “Palumas geodes” which is one of the famous types of Mexican T.E geodes which come from Chihuahua province in Northern Mexico. But real T.Es which full filled with chalcedony with show circular to horizontal banding are too rare in Gonabad nodules. These T.Es are filled with pale blue chalcedony and show weak banding.

"Click on photos for seeing more details in larger size"


Location of Gonabad thunder's egg field in Iran

Sight of Gonabad thunder's egg field hills cover with reddish rhyodacitic lava

A little complete spherical shape thunder's egg nodul.

A broken large elipsoidal shape thunder's egg geode which filled with quartz crystals

A large thunder's egg which filled with blue chalcedony, shows fine banding, and calcite in centre. 107x107 mm


A thunder's egg geode, which looks like Mexican "Palumas geodes". 62x51 mm  

A cut and polished thunder's egg geode 68x55 mm


An exploratory pit which has digged in the rhyodacitic mantlerock  

A broken elipsoidal shape thunder's egg geode which filled with quartz crystals

A large broken thunder's egg geode which filled with quartz, chacedony and calcite

An unusual little spherical thunder's egg which it's central cavity filled with a red jasper. 60x64 mm

A nodule which the volume of inner cavity is too little for hosting silica solution 47x48mm

A cut and polished thunder's egg geode 64x54 mm

Completely quartz center-filled (Frozen)

thunder's egg geode 68x76 & 45x47mm