Word of the Week – Wairakite


A zeolite mineral of hydrothermal origin that was first identified in the Wairakei geothermal field in New Zealand by Alfred Steiner. It forms clear to white prismatic crystals, which have a distinctive cross hatched twinning, and it is commonly associated with calcite and epidote. It is used as a mineral geothermometer indicating formation at >220°C.

Word of the Week – Drill Cuttings

Drill Cuttings

Small chips of rocks (e.g., <1/8 inch or <3 mm) obtained during drilling with a rotary bit that are continuously returned to the surface by the circulation of mud. Drill cuttings are the main source of geological and stratigraphic interpretation in the drilling of geothermal and oil-gas wells.

Word of the Week – Drill Core

Drill Core

Intact cylindrical shaped sample of rock obtained during drilling with a special coring bit. Although commonly narrow in diameter (e.g., 1-4" or 25-100 mm), it preserves a geological record that makes it possible to interpret the sequence of mineral formation, fracturing, and vein filling.

Did you know… there is a place where the bath water never gets cold?

Did you know... there is a place where the bath water never gets cold?

Something you might not know about Bath, England is that it was named for the thermal hot springs used as Roman baths. The natural springs were first discovered by Prince Bladud and his pigs around 863 BC. It is said he was cured from a skin disease (leprosy) after bathing in the healing waters. Subsequently, the baths were used by the Celts, Saxons, Georgians, and, of course, the Romans.

In the 17th and 18th century fashionable society found it very popular to bathe in the hot springs because of the perceived health benefits.

In the heart of the city, there are three natural springs. The biggest and most notable one is the King’s Spring, which is located in the Roman Baths Museum. The other, smaller springs, Hetling Spring and Cross Bath Spring are about 150 m west of the King’s Spring.

The thermal waters contain dissolved salts from over 40 different minerals, leading to elevated concentrations of calcium, sulphate, and chloride. The deep mineral-rich water has a constant temperature of at least 45˚C (113˚F) and the flow is approximately one million liters per day, supplying the four baths at the Thermae Bath Spa.

The bath water comes from rainfall that percolates through the soil into the underground limestone aquifers between 2,700 and 4,300 meters (8,900 and 14,100 feet) deep. Once heated, the water becomes buoyant and it flows upwards through fissures and faults to reach the surface and the baths. The hydrothermal system that provides hot water to the baths resembles an Enhanced Geothermal System (EGS), wherein hot rocks transfer energy to cold water to create geothermal power.





Word of the Week – Gneiss


Metamorphic rock that forms under intense pressure and high temperature and that is made of quartz, feldspar, amphibole and mica. Gneiss represents the highest grade of metamorphic rock, which is characterized by alternating bands of dark and light-colored minerals, foliation (i.e., parallel alignment of planar minerals) and tight folding. This rock type is common at mid to deep levels of continental crust.

Word of the Week – Rhyolite


Light colored fined grained volcanic rock composed of glass, quartz, K-feldspar and plagioclase, with relatively high silica (69-77 wt %). The composition reflects partial melting of continental crust. Rhyolitic volcanism is a feature of both Yellowstone (USA) and the Taupo Volcanic Zone (New Zealand) where geothermal activity is widespread.  The intrusive coarsely crystalline igneous rock equivalent is called granite.

Word of the Week – Basalt


Dark grey fine grained volcanic rock composed of plagioclase, pyroxene and olivine, with relatively low silica (45-52 wt %). The composition reflects an upper mantle origin. Basalt is the most common type of volcanic rock on Earth, and it erupts from mid-ocean spreading ridges and hot spots (e.g., Hawaii and Iceland). The intrusive coarsely crystalline igneous rock equivalent is called gabbro.