Tuesday, May 31, 2016

Why is massive rose quartz pink?

I have always enjoyed collecting quartz, and massive rose quartz is one of my favorites. There are some interesting new findings about what causes its coloration, and this post with help inform you about some of them. You might note that researchers use the adjective “massive” to describe rose quartz. This is done in order to differentiate it from euhedral (nice, angular crystals) of rose quartz.

A polished specimen of massive rose quartz, 3.75 inches high.

Massive rose quartz is one of the common colored varieties of quartz and found at numerous localities worldwide. A few of the areas where multiple localities are known include: Brazil, California (Riverside County), Montana, South Dakota, Norway, and Madagasgar. Massive rose quartz is commonly found in granitic pegmatities. It is less commonly found in hydrothermal veins.

Unpolished massive rose quartz (about 6.5 inches long), from Minas Gerais mine in Brazil.

So, what causes the pink color of massive rose quartz? Over the years, there have been various explanations, but the one that has been meticulously researched by Caltech mineralogists in recent years has proven the presence of pink nanofiber inclusions, which are related to the pink mineral dumortierite, a boron-bearing silicate. These pink nanofibers are 0.1 to 0.5 micro meters in width [about 0.00002 inches], and they resemble wavy bundles of hair-like fibers.

Massive rose quartz is always slightly to highly cloudy (turbid) and never clear. Its color can range from pale to pink to lavender (even in the same hand specimen, see third picture), and, in some cases, entirely lavender (see fourth picture), or, reportedly, orange.

From left to right: massive rose quartz showing transition from pale pink to pinker to lavender.
Hand specimen is 5 inches in length.

Lavender variety of massive rose quartz.
Hand specimen is 4 inches high.

I obtained much of the above information from the very informative article:  Goreva, J., C. Ma, and G. R. Rossman, 2001. Fibrous nanoinclusions in massive rose quartz: The origin of rose coloration. American Mineralogist vol. 86, pp. 466–472.

Just copy the article title, paste it in the Google Search box, and you can get your own free pdf.

Wednesday, May 18, 2016

New mud volcano in Pakistan

This post concerns a mud-volcano island created by a 7.8M earthquake in southern Pakistan on September 24, 2013. The island, called Zaizala Jazeera (or “Earthquake Mountain”) formed 1 km (0.6 mi.) offshore from the coastline in shallow-marine waters, in the Paddi Zirr (West Bay) area near Gwadar, Pakistan (25°N, 62°E).

The island was originally circular with a diameter of 250 m. The original height was 15 to 20 m (60 to 70 ft.). It is currently sinking, and has already sunken 10 ft. into the sea since first appearance. Geologists believe that the island was caused by the earthquake-related, emission of methane gas on the seabed. Corals have inhabited the slopes of the island.

For additional close-up pictures of the mud volcano,
click HERE

Friday, May 6, 2016

Nyalam area fossils age-correlative to those in the summit area of Mt. Everest (Part 3 of 3)

This third and last blog about the Mt. Everest area deals with the paleontology of beds at Nyalam that are more accessible but age equivalent to the fossiliferous beds found at Mt. Everest.

Nyalam is near a highway and 70 mi. (120 km) west of Mt. Everest.

used my figure again to help you keep track of the rock units of the Nyalam and Mt. Everest, with especial attention to the fossiliferous sedimentary rocks capping the latter.

Paleontologists have been able to trace the Everest fossiliferous sequence to the west (at more accessible altitudes) about 110 km (75 mi.) within the Chinese Nyalama area, very near the Nepal-Tibet border and northeast of Kathamandu. The Nyalama sequence is contemporaneous in age with the sedimentary sequence exposed near the summit of Everest, and the Nyalama beds, which are in the lower part of the Chiatsum Group, are rich in brachiopods, crinoids, crinoids, and reportedly some cephalopods. Work by Harper et al. (2011) in the Nyalama area has shown that the entire upper part of the Everest rock sequence above the distinctive "Yellow Band" consists of Ordovician carbonates over 200 m thick, which are correlative to the lower part of the Chiatsum Group, which is called the Qomolangma Formation at Everest. Conodonts in the lower Chiatsum Group in the Nyalam beds are indicative of the upper Darriwilian interval (upper Middle Ordovician). 

The lower Chiatsum Group in the Nyalam area represents a transgressive marine succession comprised of cycles of mid-shelf bioclastic limestones and peritidal dolomites. The entire succession was deposited in mid-shelf to deep sub tidal depths in warm, subtropical waters that were present in a low-latitude region about 30°S, in proximity to India. 

Work by Harper et al. (2011) in the Nyalam area [you can get a free pdf of this article by clicking HERE then scrolling down to pages 214–220] has shown that the entire upper part of the Everest rock sequence above the distinctive "Yellow Band" consists of Ordovician carbonates over 200 m thick, which are correlative to the lower part of the Chiatsum Group, which is called the Qomolangma Formation at Everest. In this article, there is also information concerning the macrofossils (visible to the eye) found at Nyalama.

Brachiopods dominate the fossil assemblages found in the lower Chiatsum Group in the Nayalma area. Seven genera have been 
found as of 2011. Their preservation is mostly as internal molds, so 
I found drawings of a few of them

Aporthophyla perelegans Liu, 1976 from the lower Chiatsun Formation in southern Tibet (diagram from Zhan et al., 2014.

You can get a free pdf of Zhan et al., 2014, by clicking HERE and then click on "download full text."

This brachiopod is Orthambonites sp. from Middle Ordovician rocks, Badger Pass, Death Valley, Inyo County, California. This genus, which occurs in the Nyalam area west of Mt. Everest also occurs elsewhere in the world.