1 The ridge consists entirely of volcanic rock.

2 Fresh volcanic rocks are poor conductors of electricity.

3 Thus the volcanic rocks formed are drastically different from their oceanic counterparts.

4 So volcanic rocks are composed of only a few mineral groups, each group having its own characteristic atomic structure.

5 Volcanic rocks cool quickly, trap the argon, and so give good dates.

6 The important properties of these three principal volcanic rock groups can be summarized in simple tables.

7 Most volcanic rocks contain some phenocrysts - they are a bit like the pips in raspberry jam.

8 These are frequently associated with volcanic rocks of oceanic type.

9 Basalts are examples of basic volcanic rocks,(www.Sentencedict.com) while andesites are intermediate between basic and acid.

10 RioFinex examined the Ordovician volcanic rocks of County Tyrone for base metals but found only minor intersections of low-grade copper mineralisation.

11 The codename was chosen because rhyolite is a volcanic rock containing colourful pieces of quartz set in a mass of crystals.

12 Although it is one of the most widely-known volcanic rocks, obsidian lava flows are rare.

13 Unlike most volcanic rocks, obsidian does not contain phenocrysts; it is, so to speak, all glassy groundmass.

14 Warped and folded Paleozoic strata and reddish Tertiary volcanic rocks are capped with dark Quaternary basalt flows.

15 Volcanic rock can become favorable oil - gas reservoirs.

16 It's built on volcanic rock and ash.

17 Volcanic rock includes the volcanic glass obsidian.

18 Basalt is the commonest volcanic rock.

19 The Badao deposit is a typical Mesozoic volcanic rock - hosting deposit.

20 Ciweigou deposit is one of the typical volcanic rock gold deposits in the country.

21 Crystal twinning patterns in a leucite crystal from volcanic rock, observed in polarized light by Dr. Michael M. Raith of the Steinmann Institut, University of Bonn, Bonn, Germany. (Dr.

22 Volcanic rock from two eruptive sources, Taoyuan - Hongxing and southern Dapingfang weaves and superimposes reciprocally in strata.

23 Obsidian, a form of volcanic rock valued for its strength and durability, was an important resource for ancient Mesoamerican cultures including the Zapotec and Maya.

24 The perlites are volcanic rock processed to yield an expanded form.

25 Volcanic rock is widely developed both in the vertical and horizon direction in Huanghua depression.

26 Sumatra is composed of old, thick continental crust comprising volcanic rocks of Permian, Cretaceous and Cenozoic age.

27 But it has endured because it was constructed of brick and volcanic rock between 1783 and 1792.

28 Jiamuhe formation along the northwestern margin of the Junggar basin is volcanic rock bearing stratum.

29 The carrier of the modified filter medium is the volcanic rock coated with a polycondensate modifier.

30 But, with constant launch and deepgoing of exploration work of volcanic reservoir, the research methods of reservoir connected with volcanic rock is increasingly becoming mature.