video record
Media not available in the Digital Archive
This programme is particularly concerned with the structure, properties and distribution of silicate minerals in the earth B. Wright, Reader in Earth Sciences, shows that the fundamental unit of al...l silicate structures is the silicate tetrahedron. Dr. Joan Mason, Lecturer in Chemistry, demonstrates how the basic tetrahedron can be combined together in a number of ways to form different minerals with different physical properties. The following structures are illustrated: 1. Separate tetrahedra - olivine; 2. Double chains - asbestos; 3. Sheet silicates - tale & mica; 4. Framework silicates - quartz. John Wright, at the end of the programme, shows on a cross-section of a glebe the distribution of silicate minerals with increasing depth.
Metadata describing this Open University video programme
Item code: S2-2; 02
First transmission date: 15-07-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:22:24
+ Show more...
Producer: Penny Crompton
Contributors: John Mason; John Wright
Publisher: BBC Open University
Keyword(s): Double chains - asbestos; Earth cross-section; Framework silicates - quartz; Separate tetrahedra - olivine; Sheet silicates - talc and mica; Silicate distribution and properties; Silicate structure; Silicate tetrahedron
Footage description: Joan Mason with a molecular model of the silicate tetrahedron. She uses the model to explain its composition. Joan Mason shows three different models of the Si 04 tetrahedron - space filling, ball and spoke, solid tetrahedron. She then uses an animated diagram to show the nature of the bonding - in this case an orthosilicate anion (olivine). Mason then uses a model and an assimated diagram to show how the basic tetrahedron can be combined to form structures in up to three dimensions. Mason with a model of the olivine structure. She explains the principles on which the olivines are built. She then explains how olivines can vary from pure magnesium to pure iron olivine in the same structure. Mason with a sample of asbestos fibre. Shot of photo-micrograph of asbestos fibre. She then uses a space filling molecular model to show how the silicate double chain in asbestos is formed. (Amphiboles) Joan Mason with samples of sheet silicates, talc and mica. She demonstrates the bending properties of each. Mason explains the reasons for this difference in bending properties and uses two molecular sandwich models to demonstrate. Joan Mason with two framework silicate models of quartz. She describes the properties of this silicate. Mason explains what happens when silicates are replaced by aluminates. Shot of a felspan sample. Joan Wright with a cut-away model of the earth showing the major layers (crust, mantle and core). He discusses the distribution and characteristics of silicate materials at increasing depth. Wright with samples of granite and basalt made up largely of feldspar, quartz, mica and These rocks are the main constituents of the crust. Their characteristics are shared tetrahedra. Wright discusses the mineral composition of the upper mantle. He shows a sample of peridotite which consists mainly of olivine. Wright then discusses the properties of olivines under greater pressure which are found in the lower mantle. Here the tetrahedra are compacted to octahedra. Wright uses molecular models to show this. He speculates that the lower mantle is composed of octahedral silicates.
Master spool number: 6LT/70330
Production number: 00521_2159
Videofinder number: 1645
Available to public: no