<![CDATA[1A Collections]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/browse?sort_field=added&sort_dir=a&page=22&output=rss2 Tue, 09 Apr 2024 21:25:20 +0100 p1acollections@esc.cam.ac.uk (1A Collections) Zend_Feed http://blogs.law.harvard.edu/tech/rss <![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[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[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[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[Lustre]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/220

Title

Lustre

Subject

A combination of the intensity and quality of the light reflected from the surface of a mineral. A number of terms are used to describe the range of lustres displayed by minerals, including adamantine, dull, metallic, pearly, resinous and vitreous.
]]> Fri, 21 Jun 2019 16:27:12 +0100 <![CDATA[Macrocryst]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/221

Title

Macrocryst

Subject

A relatively large crystal, usually occurring within an igneous rock. Unlike the term phenocryst, it does not imply a petrogenetic link between the crystal and the surrounding magma.

Description

Compare with phenocryst.
]]> Fri, 21 Jun 2019 16:27:52 +0100 <![CDATA[Melanocratic]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/222

Title

Melanocratic

Subject

Melanocratic rocks have a high colour index. That is to say that 60-90 vol% of the rock is made up of ferromagnesian minerals.
]]> Fri, 21 Jun 2019 16:28:13 +0100 <![CDATA[Mesocratic]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/223

Title

Mesocratic

Subject

Mesocratic rocks have a moderate colour index. That is to say that 30-60 vol% of the rock is made up of ferromagnesian minerals.
]]> Fri, 21 Jun 2019 16:29:04 +0100 <![CDATA[Metallic [lustre]]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/224

Title

Metallic [lustre]

Subject

Minerals displaying a metal-like lustre are described as metallic. These minerals have surfaces which are perfectly reflective. Pyrite, for example, has metallic lustre.

Description

Have a look at pyrite (M520) in the 1A Reference Series.
]]> Fri, 21 Jun 2019 16:30:54 +0100 <![CDATA[Micaceous]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/225

Title

Micaceous

Subject

A rock containing a significant proportion of micas is described as micaceous. The micas are a group of sheet silicate minerals, which include biotite and muscovite.

Description

Have a look at muscovite mica (M301, M302) and biotite mica (M303, M304) in the 1A Reference Series.
]]> Fri, 21 Jun 2019 16:35:01 +0100