Andesite Tuff

Title

Andesite Tuff

Identifier

TMJ-18

Description

Rock Sample:
The color is mainly blue and black. The sample is aphanitic and the cross section of the sample reveals very fined grained phenocrysts (~1mm in diameter). The colors of the phenocrysts range from white, blue, black, or green.
It has rough sandy feel to it. There is some major chemical weathering. There is some white residue on the surface which has a minor reaction to Hydrochloric acid.
-Hardness = 5.5
-Streak = The dark spots on the sample had a dark-brownish to yellow streak, while the blue part of the sample did not have a streak.

Thin Section:
Oxidation is shown in the thin section. The matrix has blue swells. Some of the pyroxene crystals are very fine grained and show exhibit a "swirly" texture. The plagioclase crystals exhibit some crytsal-zoning. The sample is hypocrystalline. Others are fractured and filled in with very fine grained matrix. There are large fractures within the pyrozene crystals as well. Matrix is intergrown into coarse grained quartz.
-Quartz (40%)
-Pyroxene (25%)
-K-feldspar (20%)
-Plagioclase (15%)
-Magnification at 4x/0.10

Scanning Electron Microscope:
The blue mineral that is found through out the sample is made up of silicon, oxygen, carbon, calcium, sodium, and aluminum.

Date

1969

Contributor

Western Minerals, Inc.

Spatial Coverage

Tanzawa Mountains, Japan Rifle range and Inn near Kajaka (SE side of intrusive)

Temporal Coverage

N/A

Accrual Method

Purchased from Western Minerals Inc.

Unit

N/A

Number of Thin Sections

1

Geolocation