Basaltic andesite ash (field of view ~5.2 cm across) from a 14 June 2006 block & ash flow (pyroclastic flow) from Mt. Merapi.
Locality: pyroclastic flow deposit at ~1200 meters elevation in the hamlet of Bebeng, village of Kaliadem, ~30 km from Yogyakarta, central Java, Indonesia (7º 34’ 57” South, 110º 26’ 51” East).
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One of the more recently active volcanoes is Mt. Merapi in central Java Island, Indonesia. Mt. Merapi has had frequent eruptions for at least the last 2000 years, with relatively quiet intervals at ~600-700 years ago & at ~1100-1400 years ago (see Gertisser & Keller, 2003). Between 20 and 30 eruption intervals have been recorded in the 1800s and in the 1900s. From May to June 2006, Merapi was observed to issue lava flows, ash columns, and ash flows.
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Some info. from:
Gertisser & Keller (2003) - Temporal variations in magma composition at Merapi Volcano (central Java, Indonesia): magmatic cycles during the past 2000 years of explosive activity. Journal of Volcanology and Geothermal Research 123: 1-23.
Tags: Merapi basaltic andesite 2006 pyroclastic flow volcanic ash eruption Indonesia Java
Sulfidic travertine from the upper Cenozoic of Indonesia.
This attractive material is called "Bumblebee Jasper" or "Mustard Jasper", in reference to its color. "Jasper" is a rockhound/lapidarist term for finely crystalline quartz, but Bumblebee Jasper is not quartz - it bubbles in acid. Chemical analysis has confirmed that it is calcium carbonate (CaCO3 - calcite). The coloration is from various microscopic mineral inclusions. The light to medium gray areas are ~inclusion-free calcite. The dark gray to black bands are from pyrite inclusions (FeS2 - iron sulfide, also known as "fool's gold"). The yellowish and orangish areas are from realgar inclusions. Realgar is a reddish-colored arsenic sulfide mineral (AsS). In the form of very small, disseminated inclusions, it has a yellowish-orangish color.
Bumblebee Jasper has a finely-, but irregularly-banded structure. The calcite itself is fibrous. Banded, fibrous calcareous rocks are known as travertine, which is a chemical sedimentary rock. Travertine is commonly encountered in caves, in the form of speleothem - stalactites, stalagmites, columns, flowstone, etc. Travertine also forms at many hot springs. Bumblebee Jasper appears to be travertine deposited in a volcanic solfatara area, with signficant iron, arsenic, and sulfur impurities.
The deposit is reported to be near the base of Mount Papandayan, a subduction zone stratovolcano in Indonesia. However, I have seen no site descriptions, locality photos, or detailed maps. I have been told that the Mt. Papandayan locality information is inaccurate, and that Bumblebee Jasper is found at three sites in western Java: near the town of Ciniru (Kuningan Regency), near the town of Cirebon, and in the Bandung area.
Locality: unrecorded/undisclosed in Indonesia (but attributed to near Mount Papandayan, western Java)
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See info. at:
Fritsch & Ivey (2015) - Mustard Jasper or Bumble bee stone. 34th International Gemmological Conference, August 2015, Vilnius, Lithuania: 149-150. (pdf - see pages 149 to 150 of this file: static1.squarespace.com/static/5d820bb8a789f32f58d708c5/t...)
Tags: sulfidic travertine calcite pyrite realgar arsenic iron sulfur sulfide sulfides mineral minerals Bumblebee Bumble Bee Jasper Mustard Mount Mt. Papandayan subduction zone stratovolcano volcano West Java Indonesia
Sulfidic travertine from the upper Cenozoic of Indonesia.
This attractive material is called "Bumblebee Jasper" or "Mustard Jasper", in reference to its color. "Jasper" is a rockhound/lapidarist term for finely crystalline quartz, but Bumblebee Jasper is not quartz - it bubbles in acid. Chemical analysis has confirmed that it is calcium carbonate (CaCO3 - calcite). The coloration is from various microscopic mineral inclusions. The light to medium gray areas are ~inclusion-free calcite. The dark gray to black bands are from pyrite inclusions (FeS2 - iron sulfide, also known as "fool's gold"). The yellowish and orangish areas are from realgar inclusions. Realgar is a reddish-colored arsenic sulfide mineral (AsS). In the form of very small, disseminated inclusions, it has a yellowish-orangish color.
Bumblebee Jasper has a finely-, but irregularly-banded structure. The calcite itself is fibrous. Banded, fibrous calcareous rocks are known as travertine, which is a chemical sedimentary rock. Travertine is commonly encountered in caves, in the form of speleothem - stalactites, stalagmites, columns, flowstone, etc. Travertine also forms at many hot springs. Bumblebee Jasper appears to be travertine deposited in a volcanic solfatara area, with signficant iron, arsenic, and sulfur impurities.
The deposit is reported to be near the base of Mount Papandayan, a subduction zone stratovolcano in Indonesia. However, I have seen no site descriptions, locality photos, or detailed maps. I have been told that the Mt. Papandayan locality information is inaccurate, and that Bumblebee Jasper is found at three sites in western Java: near the town of Ciniru (Kuningan Regency), near the town of Cirebon, and in the Bandung area.
Locality: unrecorded/undisclosed in Indonesia (but attributed to near Mount Papandayan, western Java)
-----------------------------
See info. at:
Fritsch & Ivey (2015) - Mustard Jasper or Bumble bee stone. 34th International Gemmological Conference, August 2015, Vilnius, Lithuania: 149-150. (pdf - see pages 149 to 150 of this file: static1.squarespace.com/static/5d820bb8a789f32f58d708c5/t...)
Tags: sulfidic travertine calcite pyrite realgar arsenic iron sulfur sulfide sulfides mineral minerals Bumblebee Bumble Bee Jasper Mustard Mount Mt. Papandayan subduction zone stratovolcano volcano West Java Indonesia
Sulfidic travertine from the upper Cenozoic of Indonesia.
This attractive material is called "Bumblebee Jasper" or "Mustard Jasper", in reference to its color. "Jasper" is a rockhound/lapidarist term for finely crystalline quartz, but Bumblebee Jasper is not quartz - it bubbles in acid. Chemical analysis has confirmed that it is calcium carbonate (CaCO3 - calcite). The coloration is from various microscopic mineral inclusions. The light to medium gray areas are ~inclusion-free calcite. The dark gray to black bands are from pyrite inclusions (FeS2 - iron sulfide, also known as "fool's gold"). The yellowish and orangish areas are from realgar inclusions. Realgar is a reddish-colored arsenic sulfide mineral (AsS). In the form of very small, disseminated inclusions, it has a yellowish-orangish color.
Bumblebee Jasper has a finely-, but irregularly-banded structure. The calcite itself is fibrous. Banded, fibrous calcareous rocks are known as travertine, which is a chemical sedimentary rock. Travertine is commonly encountered in caves, in the form of speleothem - stalactites, stalagmites, columns, flowstone, etc. Travertine also forms at many hot springs. Bumblebee Jasper appears to be travertine deposited in a volcanic solfatara area, with signficant iron, arsenic, and sulfur impurities.
The deposit is reported to be near the base of Mount Papandayan, a subduction zone stratovolcano in Indonesia. However, I have seen no site descriptions, locality photos, or detailed maps. I have been told that the Mt. Papandayan locality information is inaccurate, and that Bumblebee Jasper is found at three sites in western Java: near the town of Ciniru (Kuningan Regency), near the town of Cirebon, and in the Bandung area.
Locality: unrecorded/undisclosed in Indonesia (but attributed to near Mount Papandayan, western Java)
-----------------------------
See info. at:
Fritsch & Ivey (2015) - Mustard Jasper or Bumble bee stone. 34th International Gemmological Conference, August 2015, Vilnius, Lithuania: 149-150. (pdf - see pages 149 to 150 of this file: static1.squarespace.com/static/5d820bb8a789f32f58d708c5/t...)
Tags: sulfidic travertine calcite pyrite realgar arsenic iron sulfur sulfide sulfides mineral minerals Bumblebee Bumble Bee Jasper Mustard Mount Mt. Papandayan subduction zone stratovolcano volcano West Java Indonesia
"Grape agate" - amethyst & purple chalcedony from the Tertiary of Indonesia. (~9.0 centimeters across at its widest)
A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 5700 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.
The silicates are the most abundant and chemically complex group of minerals. All silicates have silica as the basis for their chemistry. "Silica" refers to SiO2 chemistry. The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4. Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens "belong" to each silicon. The resulting formula for silica is thus SiO2, not SiO4.
The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2). All other silicates have silica + impurities. Many silicates have a significant percentage of aluminum (the aluminosilicates).
Quartz (silicon dioxide/silica - SiO2) is the most common mineral in the Earth's crust. It is composed of the two most abundant elements in the crust - oxygen and silicon. It has a glassy, nonmetallic luster, is commonly clearish to whitish to grayish in color, has a white streak, is quite hard (H≡7), forms hexagonal crystals, has no cleavage, and has conchoidal fracture. Quartz can be any color: clear, white, gray, black, brown, pink, red, purple, blue, green, orange, etc.
Purple quartz is called amethyst. The coloring agent for amethyst is not agreed upon. Some workers say that it is due to Fe+4 impurity, some say the impurity is Fe+3, and others say it is Mn.
The cluster of purplish rounded masses seen here is "grape agate" or "grape chalcedony". In reality, it's finely crystalline amethyst, although analysis has shown that purple chalcedony is also present.
This material appears to be hydrothermal in origin and occurs along the altered/degraded margins of Miocene-aged, porphyritic trachyandesite pillow lavas.
Locality: mine in the mountains of the Mamuju area, West Sulawesi Province, Sulawesi, Indonesia
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Photo gallery of quartz and amethyst and grape agate:
www.mindat.org/gallery.php?min=3337
and
www.mindat.org/gallery.php?min=198
and
www.mindat.org/gallery.php?min=51479
Tags: amethyst purple chalcedony Tertiary Sulawesi Indonesia quartz hydrothermal