https://wserv3.esc.cam.ac.uk/p1acollections/items/browse?page=17&sort_field=added&sort_dir=a&output=atom <![CDATA[1A Collections]]> 2024-04-09T21:24:18+01:00 Omeka https://wserv3.esc.cam.ac.uk/p1acollections/items/show/166 <![CDATA[<h2>Adamantine [lustre]</h2>]]> 2019-07-04T09:52:56+01:00

Title

Adamantine [lustre]

Subject

Minerals displaying a diamond-like lustre are described as adamantine. These minerals are transparent or translucent and have very high refractive indices, producing the high degree of lustre. Zeolites, for example, have adamantine lustre.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/167 <![CDATA[<h2>Aeolian</h2>]]> L326) in the 1A Reference Series.]]> 2019-07-04T09:52:56+01:00

Title

Aeolian

Subject

Relating to or arising from the action of the wind; aeolian sediments are wind-blown. Also spelt eolian.

Description

Have a look at the ferruginous arenite sandstone (L326) in the 1A Reference Series.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/168 <![CDATA[<h2>Albite twinning</h2>]]> 2019-07-04T09:52:56+01:00

Title

Albite twinning

Subject

Named after albite (Na-plagioclase) twinning on the (010) crystallographic plane.
See lamellar twinning.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/169 <![CDATA[<h2>Lamellar twinning</h2>]]> 2019-07-04T09:52:57+01:00

Title

Lamellar twinning

Subject

Many parallel twins can be produced within one mineral grain by multiple parallel twin planes. This is known as lamellar twinning. It is a diagnostic characteristic of plagioclase feldspar, and is sometimes referred to as albite twinning.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/170 <![CDATA[<h2>Alteration</h2>]]> Common alteration minerals include clays for plagioclase, serpentine for olivine, and chlorite for ferromagnesian minerals such as biotite.]]> 2019-07-04T09:52:57+01:00

Title

Alteration

Subject

Rocks undergo mineralogical change at low pressures, produced by reactions with circulating fluids. The replacement of the original minerals in the rock tends to take place primarily along cracks and around the edges of grains, though whole mineral grains can be replaced. The decomposition of olivine to serpentine is a common example of alteration.

Description

Common alteration minerals include clays for plagioclase, serpentine for olivine, and chlorite for ferromagnesian minerals such as biotite.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/171 <![CDATA[<h2>Amorphous</h2>]]> Have a look at the rhyolite glass (L113) in the 1A Reference Series.]]> 2019-07-04T09:52:57+01:00

Title

Amorphous

Subject

Amorphous materials are non-crystalline solids. That is to say that they do not display long-range order in their structures. Glass is amorphous.

Description

Have a look at the rhyolite glass (L113) in the 1A Reference Series.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/172 <![CDATA[<h2>Amygdale</h2>]]> Have a look at the amygdaloidal basalt (L161) in the 1A Reference Series.]]> 2019-07-04T09:52:57+01:00

Title

Amygdale

Subject

A vesicle (necessarily in an igneous rock), which has been filled in by a mineral crystallising from late-stage fluids. Amygdales are commonly produced by the crystallisation of quartz, calcite or zeolite.

Description

Have a look at the amygdaloidal basalt (L161) in the 1A Reference Series.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/173 <![CDATA[<h2>Anhedral</h2>]]> Have a look at the granodiorite (L120) for anhedral quartz, biotite and plagioclase.]]> 2019-07-04T09:52:58+01:00

Title

Anhedral

Subject

A crystal displaying none of its characteristic crystal faces is called anhedral.

Description

Have a look at the granodiorite (L120) for anhedral quartz, biotite and plagioclase.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/174 <![CDATA[<h2>Anisotropic</h2>]]> Compare with isotropic.]]> 2019-07-04T09:52:58+01:00

Title

Anisotropic

Subject

The speed of light through any medium is inversely proportional to the refractive index of the medium. The refractive index of a mineral is determined by the arrangement and type of atoms within its structure.

If the structure of the mineral allows light to travel at different velocities depending on the direction in which the light is passing through it, the mineral is anisotropic. That is to say, it has different refractive indices in different orientations.

Description

Compare with isotropic.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/175 <![CDATA[<h2>Aphanitic (or aphyric)</h2>]]> 2019-07-04T09:52:58+01:00

Title

Aphanitic (or aphyric)

Subject

Igneous rocks made up of grains too small to be seen with the naked eye have an aphanitic texture. These rocks do not contain phenocrysts. They are non-porphyritic.
]]>