<![CDATA[1A Collections]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/browse?page=6&sort_field=added&sort_dir=d&output=rss2 Tue, 09 Apr 2024 21:21:52 +0100 p1acollections@esc.cam.ac.uk (1A Collections) Zend_Feed http://blogs.law.harvard.edu/tech/rss <![CDATA[Lineation]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/219

Title

Lineation

Subject

This refers to any pervasive linear feature in a rock. It can be produced by the intersection of two foliations (planar rock fabrics) or by the alignment of linear objects such as elongate grains in the rock. Linear fabrics can be primary (e.g. flow lineations) or secondary (e.g. mineral alignment during metamorphism).

lineation_1.png
lineation_2.png
]]> Fri, 21 Jun 2019 16:26:35 +0100 <![CDATA[Leucocratic]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/218

Title

Leucocratic

Subject

Leucocratic rocks have a low colour index. That is to say that <30 vol% of the rock is made up of ferromagnesian minerals.

]]> Fri, 21 Jun 2019 16:24:59 +0100 <![CDATA[Length slow]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/217

Title

Length slow

Subject

All anisotropic minerals have fast and slow vibration directions. If the slow vibration direction is parallel to the direction of elongation of the crystal, it is said to be length slow.

Description

Compare with length fast.
length_fast.png
]]> Fri, 21 Jun 2019 16:23:44 +0100 <![CDATA[Length fast]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/216

Title

Length fast

Subject

All anisotropic minerals have fast and slow vibration directions. If the fast vibration direction is parallel to the direction of elongation of the crystal, the crystal is length fast.

Description

Compare with length slow.
length_fast.png
]]> Fri, 21 Jun 2019 16:22:39 +0100 <![CDATA[Lath]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/215

Title

Lath

Subject

A crystal with an elongate, needle-like form is said to be lath-shaped. This term is most commonly applied to elongate crystals of feldspar in igneous rocks.
]]> Fri, 21 Jun 2019 16:20:25 +0100 <![CDATA[Kinks]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/214

Title

Kinks

Subject

These are bands of deformation in which the orientation is changed due to slipping on several parallel slip planes. Kinks can occur in a single crystal or in foliated rock.
]]> Fri, 21 Jun 2019 16:19:38 +0100 <![CDATA[Isotropic]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/213

Title

Isotropic

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 the same velocity through the mineral in all orientations, the mineral is isotropic. That is to say, it has the same refractive index in all directions. Under cross-polarised light isotropic minerals always appear black. Garnet is an isotropic mineral

Description

Compare with anisotropic.
]]> Fri, 21 Jun 2019 16:18:32 +0100 <![CDATA[Intrusive]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/212

Title

Intrusive

Subject

Rocks which have formed by the intrusion of igneous material below the surface of the Earth are described as intrusive.

Description

Compare with extrusive.
]]> Fri, 21 Jun 2019 16:16:41 +0100 <![CDATA[Interstitial]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/211

Title

Interstitial

Subject

An igneous texture in which large anhedral grains fill the gaps between earlier crystallising phases.

Description

Have a look at the granodiorite (L120) in the 1A Reference Series.
]]> Fri, 21 Jun 2019 16:15:37 +0100 <![CDATA[Inclusion]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/210

Title

Inclusion

Subject

As a crystal grows in a magma, tiny blobs of melt can become trapped in its structure. These are melt inclusions. Small crystals of other minerals can also become trapped. These are mineral inclusions.

Description

Have a look at the alkali basalt (L100), the porphyritic rhyolite (L110) and the garnet schist (L504) in the 1A Reference Series.
]]> Fri, 21 Jun 2019 16:13:23 +0100